How do I get the Love Balls?

I'm playing Shining Pearl and my girlfriend gave me a Ralts egg in a Love ball, but I can only find Poke Balls, Ultra Balls, Great Balls, Dusk Balls and some others from the shops. Who do I talk to for trading for the Love Balls? I also could not find a trader for them in the underground sphere area.

Here is a picture of it in the status menu:
picture of pokemon ball in status menu. ball is pink on top and white on the bottom. the top has a white heart outline and a vertical line in the middle


Solution 1:

The Pokéball your Raltz is in is known as the Love Ball.

Based on various guides, the Love Ball does not appear to be obtainable from any vendor within the game. The Love Ball was a pre-order bonus by pre-ordering the game through various vendors in the US and the UK, and redeemable codes in Japan.