As I said, don't buy clothes that she will wear when with him. Send her in the clothes on her back.
You are going to have to force his hand here.
If he refuses to buy clothes (or footwear, etc) for her, take him to court and revisit the 50-50 arrangement. He needs to pay, one way or the other, for his child's needs. If you are splitting CB, then he is benefiting financially from the arrangement even more than the lack of child support payments.
She's not camping in his house when she's with him. She's living in what should be her other home. Therefore she should have clothes, pajamas, underwear, socks, swimsuit, dressing gown, slippers, school uniform, PE kit, sport clothes, outerwear for different weather conditions, footwear, books, hobby stuff, craft stuff, and all the soap, shampoo, conditioner, etc, that she needs, at his house.