Is there a way to retrieve a list of items which you have more than one copy?

Solution 1:

Use tf2ls and choose the "Extras" option, or "Text Output" for text instead of icons.

Solution 2:

You could use TF2Toolbox and set it to Plaintext and look for 'x2' and 'x3', etc.

Solution 3:

Opening the crafting interface, going to the last tab and choosing Custom Blueprint (last option), then selecting one of the empty boxes at the right will show you how many of each item you have.

Beware, though, that it doesn't always separate out the different qualities of items.

Solution 4:

Actually, tf2items.com does offer this. Go to tf2items.com and enter you profile ID. (If you don't have a profile ID set up, just copy the link to your community page)

On your backpack page it will show 3 different tabs, the last one - checklist - should be exactly what you need.