They look the same as the child sized belts I bought for Cloud's KH1 outfit:
They are around the calves and around one thigh.
I bought them at walmart.
Anyway, you might be able to use those but IDK. Another idea is to still use them, but ONLY the buckles. Buy them and cut the buckles out (I've never seen buckles that look like that, that are that small, not already attached to belts that were worth the price, these are like $2 each..). Then buy some vinyl from the fabric store in the right color and sew the buckle on and make them like this:
You would sew the far left end and the far right end onto the waist line of the shorts, then buckle them together like belts.