Because everyone else said plushies or neocash cards (which I think is boring. its just a gift card...). You could always try the neopet trading cards. You can find them on Amazon for less than $10. It might be a fun way to add a bit of Neopets while still being able to give them other things.

Or if you really want to feed into our nostalgia bone, you can always try to find one of these tomogachi type things.

Neopets is kind of past its heyday so finding great merchandise can be sort of hit or miss but like everyone else said, there's always Ebay (or Amazon has some neopet plushies) and gift cards to fall back on.