Oh no! Patagonia, this sounds so incredibly frustrating. I'm picky about clothes too, and my weight fluctuates a lot... I can't imagine someone constantly trying to buy things for me, especially things that can't be returned.
You mentioned that he loves to buy things on sale... it sounds like he takes a lot of pride in getting a good deal? Do you think that's driving it, more than wanting to buy you clothes?
Maybe that's an approach to take with him? Either talking to him about the fact that, no matter how great the deal is, it's still a waste of money if you can't use the clothes... or trying to redirect him - "Sweetie, you're so amazing at finding good deals... instead of clothes, I was wondering if you could try to find ___" (fill in the blank with something you actually want/need and can use)?
I guess the other option is to learn to sell on Ebay? Maybe he can go out and find great closeout deals, you can turn around and sell them, and between the two of you, you could make a bit of profit?

(I know, I wouldn't want to have to deal with it either - but if you're inclined to try something like that...)
Ooh! And - have you read the book about the five love languages? You might want to take a look at that (and then ask him to read it too). I wonder if his love language is something like "gifts" - and yours isn't? Just another random thought.
Ugh - anyway, I'm sorry. It sounds so frustrating, and the fact that it's still happening, a year later - just no. Have you tried the horribly blunt approach? He hands you a present, you open it, find clothes, and hand it right back ("I love that you're trying, but as we discussed, I prefer to buy my own clothes. Please return these.") - It feels rude, but I think it's fair if you've had this conversation several times and he's not getting it. Plus, it then puts the burden on him to deal with the clothes...
Sorry again!!! That would drive me right up the wall!