I don't have suggestions. I had the same experience and basically just kept hoping that my kids would cycle through their wardrobe til they got to their nicer stuff. Since they stay the night, they arrive in clothes they wore at their mom's house and leave in stuff from mine, so our stuff kind of cycles through both houses. If there are times you need nice clothes, just say..."we're going to church could I get ahold of 'x' outfit since he doesn't have any dress clothes over here." Or just tell her that because he changes out of his uniform (I presume that's what happens) then goes to your house, I end up with no clothes over here. Could I get a couple nice sets? Or you can change him back to whatever he was wearing when you picked him up and send him back in that.
In the end, it's not the years in your life that count. It's the life in your years. Abraham Lincoln
It is hard to fail, but it is worse never to have tried to succeed. Theodore Roosevelt