Honestly, if this was me, I'd just provide him with one new outfit a month, to feel like he has decent clothes to wear once in a while. We would constantly let SD wear the clothes we bought her to BM's house, only to have them never return. It used to drive me crazy, but I simply set a budget for how much we would spend on SD's clothes each month, and once that was gone it was it. I did get pushback from DH, who thought we weren't spending enough (because SD complained). But, for example, of BM was picking SD up to go to dinner we would let her wear something nice from our house and it would never return. I remember many brand new items never coming back. Then BM would send SD over in the rattiest, cheapest clothes she could find. DH said when he picked SD up BM would literally make her strip by the door if she was wearing something BM thought was "too good" to come to our house. It's not a battle worth fighting, in my opinion. It was just BM being petty, and it's pretty sad when you have to treat your kid like that to get back at your ex, in my opinion.

My DH has fought this battle for SS8 - he comes to our house with holes in his socks and underwear, or underwear that is too tight. So we go out and get him new and the mindset is that the kid shouldn't have to suffer just because the BM is an asshole. But, DH finally told her about herself and the clothing situation and it really hasn't been a problem since. It may sound bad, but if I see anything that looks in poor shape (underwear or socks), I was everything, take a picture showing the shape and then send it home. Then wait. If it comes back the next time, she gets an ear full. Now that she knows we're looking though, haven't needed to yell about it...yet. I definitely think your DH needs to speak up and find out what the issue is, no matter what their relationship is.

As for you, there are a couple ways to approach it. You could get the kid some 2nd-hand clothes from goodwill or yardsales and even get some that are bigger sizes so as the kid grows, you're not constantly going out and spending money. I also shop for the next year sizes at the end of the season to get the cheapest deals.

So now that you have clothes, the question is - do i send him home in the new stuff? or do i put him back in the stuff BM sent him in? This is a double edged sword but either way, do what gives you the most peace. You can get some pretty cheap outfits, even from the dollar store, to send him home in if you want to keep the nicer outfits at your home. Plenty of options here.