Totally agree with Chrissies reply on this one, I'd even go one step further...
Any good respectful safe client should not really ask a service provider to do oral without a condom. If they do then just how good a client are they ?? To ask at all shows that they really don't care at all about the health and safety of either the service provider or themselves. I would hope the majority of service providers would tell such clients to "p@#$ off" and hope that management of well run professional establishments would discourage such clients from returning....
All the best
The Ruler