considering my niche, it's very common.  I don't think you'd have many issues as long as it wasn't a surprise.

I'm not a provider, just a man whore...

Common sense tells me that pulling out a penis pump on a younger hooker might throw her off.
Dick ring? Not so much..
Older more seasoned hooker? You are good.

They compliment our pleasure

I have used a cock ring once to hold the rubber on during sex. It worked great no problems of it coming off during or after the pop.

I have never personally used a penis pump in a session, but I have been with a gent who used one.  Not sure they are worth their bang as they can be quite costly, but they certainly are interesting and isn't good sex about being open trying new things? As for cock rings and lassos, I like them...they can help the rock hardness factor and make the finale quite intense for you.

Got one of the silicon models from Liberator for $9 that's stretchy enough to go around the cock & balls at once.  Makes for a very different experience!  Haven't used it for just a BJ yet, but that's on the list to try at some point.

Tried the more rigid c-rings made by Tantus at $25 apiece, but didn't like them.

I have them at my incall

I keep cock rings at my incall, it's great for older gents and for guys that are just too physically tried to get it up. They work,try it.