if you looking to buy domains then u need to create in bst domain sales section if u want to reg using paypal then u can use dynadot , namecheap using paypal
You can buy a domain name with pay pal on some hosting sites but make sure if they offer a cheap domain names to check what the price of domain name is after that. Some sites have low cost domain names for first year than charge alot more after that.
Do you want to register a new domain or to buy a registered domain? If you to register a new domain you can try www.OrderDN.com (You can register domains at a cheap price, for each domain you will get also free host!) If you want to buy registered domains you just check the "buy, sell and trade" section Thank you