K-girls won't allow it. Believe me I have asked few of my ATFs in past. Ask girl respectfully and they will decline respectfully most likely. Don't ask POs. You might get blacklisted.
Do a keyword search on PD website to get quick listings who allow
I agree. Don't ask the PO over doing something questionable, only the provider. If you ask the PO if ok to video, they might think you might surreptiously try to do it. If you ask the provider, she will be alerted to surreptious recording and may look at or stash your phone to prevent video recording, but won't report the ask. Because I carry my phone in breast pocket, I've had providers paranoid about being recorded check I'm not recording anything.
Most provider's, I think don't like to rat out mongers for pushing limits especially if they ask nicely since they live in the world of variable sexual boundaries for both monger and provider. Can she suck on my dick without condom, can she rim me? Can I stick my finger in your ass while I fuck you? Can I fuck you in your ass? Etc. Of course a lot of these, verbal asking isn't necessary, just signaling don't go there, moving hand away, etc. But don't ask to video, then try to be sneaky, that will get you blacklisted.