WooCommerce Variations as Radio Buttons

is it possible within WooCommerce to change the variations dropdown into radio buttons without having to work with a plugin? I would like to have the following setup on the variations section:

• 1 liter (10€)
• 2 liter (20€)
• 3 Liter (25€)

The price at the bottom should be automatically changed when you select an option.

Thank you

EDIT: added variation_check() and JS variation checking thanks to @ThomasB!

EDIT2: make sure variation_check() also checks for backorder status to allow selection when a product can be backordered.

The best way I managed to get this working is to add radio button markup directly after the select dropdowns and then hide the select dropdowns using CSS. You'll also need some custom JS to trigger the hidden select value changes so that your price will change according to the radio button you select.

Here's how I added the markup:

function variation_radio_buttons($html, $args) {
  $args = wp_parse_args(apply_filters('woocommerce_dropdown_variation_attribute_options_args', $args), array(
    'options'          => false,
    'attribute'        => false,
    'product'          => false,
    'selected'         => false,
    'name'             => '',
    'id'               => '',
    'class'            => '',
    'show_option_none' => __('Choose an option', 'woocommerce'),
  ));

  if(false === $args['selected'] && $args['attribute'] && $args['product'] instanceof WC_Product) {
    $selected_key     = 'attribute_'.sanitize_title($args['attribute']);
    $args['selected'] = isset($_REQUEST[$selected_key]) ? wc_clean(wp_unslash($_REQUEST[$selected_key])) : $args['product']->get_variation_default_attribute($args['attribute']);
  }

  $options               = $args['options'];
  $product               = $args['product'];
  $attribute             = $args['attribute'];
  $name                  = $args['name'] ? $args['name'] : 'attribute_'.sanitize_title($attribute);
  $id                    = $args['id'] ? $args['id'] : sanitize_title($attribute);
  $class                 = $args['class'];
  $show_option_none      = (bool)$args['show_option_none'];
  $show_option_none_text = $args['show_option_none'] ? $args['show_option_none'] : __('Choose an option', 'woocommerce');

  if(empty($options) && !empty($product) && !empty($attribute)) {
    $attributes = $product->get_variation_attributes();
    $options    = $attributes[$attribute];
  }

  $radios = '<div class="variation-radios">';

  if(!empty($options)) {
    if($product && taxonomy_exists($attribute)) {
      $terms = wc_get_product_terms($product->get_id(), $attribute, array(
        'fields' => 'all',
      ));

      foreach($terms as $term) {
        if(in_array($term->slug, $options, true)) {
          $id = $name.'-'.$term->slug;
          $radios .= '<input type="radio" id="'.esc_attr($id).'" name="'.esc_attr($name).'" value="'.esc_attr($term->slug).'" '.checked(sanitize_title($args['selected']), $term->slug, false).'><label for="'.esc_attr($id).'">'.esc_html(apply_filters('woocommerce_variation_option_name', $term->name)).'</label>';
        }
      }
    } else {
      foreach($options as $option) {
        $id = $name.'-'.$option;
        $checked    = sanitize_title($args['selected']) === $args['selected'] ? checked($args['selected'], sanitize_title($option), false) : checked($args['selected'], $option, false);
        $radios    .= '<input type="radio" id="'.esc_attr($id).'" name="'.esc_attr($name).'" value="'.esc_attr($option).'" id="'.sanitize_title($option).'" '.$checked.'><label for="'.esc_attr($id).'">'.esc_html(apply_filters('woocommerce_variation_option_name', $option)).'</label>';
      }
    }
  }

  $radios .= '</div>';
    
  return $html.$radios;
}
add_filter('woocommerce_dropdown_variation_attribute_options_html', 'variation_radio_buttons', 20, 2);

function variation_check($active, $variation) {
  if(!$variation->is_in_stock() && !$variation->backorders_allowed()) {
    return false;
  }
  return $active;
}
add_filter('woocommerce_variation_is_active', 'variation_check', 10, 2);

And here's the JS I used:

$(document).on('change', '.variation-radios input', function() {
  $('.variation-radios input:checked').each(function(index, element) {
    var $el = $(element);
    var thisName = $el.attr('name');
    var thisVal  = $el.attr('value');
    $('select[name="'+thisName+'"]').val(thisVal).trigger('change');
  });
});
$(document).on('woocommerce_update_variation_values', function() {
  $('.variation-radios input').each(function(index, element) {
    var $el = $(element);
    var thisName = $el.attr('name');
    var thisVal  = $el.attr('value');
    $el.removeAttr('disabled');
    if($('select[name="'+thisName+'"] option[value="'+thisVal+'"]').is(':disabled')) {
      $el.prop('disabled', true);
    }
  });
});

I don't know how to do that without a plugin, but I suggest you drop that requirement, and use the Woocommerce Radio Buttons plugin. This does exactly what you want:

You can use Variation Swatches for WooCommerce plugin. It worked for me.