I'm new to the hobby and have only seen ten providers and the first seven readily agreed to use the female condom but the last three refused and I have now decided to only see providers who will use a female condom but was wondering if asking about this in the first email contact is considered explicit talk?
What's the best way to broach this subject before seeing a provider?

Simply because it implies there will be sexual activities occurring when you meet.  I would suggest that you read reviews to see if the FC is mentioned in them.  Unfortunately, I can't think of how to ask about it prior to making a date with a provider without getting hungup on or no response to an email.  Maybe some of the ladies can help.....

Swim

If you can not get the information, the only other thing I can think of is to bring a sealed package of FCs to the session and ask her if she would consider using same.

If she is unfamiliar with them, she may not want to.

That's the best I can come up with right now.

It might be a good idea if the providers' profile pages had a listing for this.

Post in the ISO section on the local boards & you will not only help yourself but also other gents that are looking for that info.