You can buy names through the Name Silo market place, and pay with Bitcoins. I sell domain names for Bitcoin as well.
If you mean register a domain name, then Name Silo also takes Bitcoin as payment for registration fees. You can also get a $1 off your first order if you use the promotion code HOTNAMES. I've got about 300 names with them, and I'm moving more to them over the next few months.
If you want to use my affiliate link, it is -
https://www.namesilo.com/pricing.php?rid=03fa233dxThat will take you to the pricing page. - .com transfers are $8.39, and that includes free privacy.
Could not manage BTC payment, but have use your affiliate link and get $1 off. Thank you!