HitBTC has B2X listed in their deposit/withdrawal section but it currently seems to be disabled. YoBit also has B2X listed in their deposit section but displays "No free addresses for such currency. Please try again in 2 minutes." every time I try to generate one.

I used their services to extract sbtc from my ledger in segwit wallet. The whole process from first contact to having the funds available on gate.io was about 20 hours. I would recommend them if you a) can't be bothered or b) don't know how to do it yourself.

Thanks!