hello "iwantotryit",
And how totally cool that you do!("wanto" that is
I know on the erosguide there's a line that says  "available to": (men,women,cpls. groups etc..)I would guess that's as good a place as any to start? Being a male it doesn't come into play so much for me but I do notice from time to time if an advertiser specifies she's available to women & cpls.
Wishing you all the best in your search!

i believe some see couples... so i assume those providers would be willing

many transsexuals do not under any circumstances entertain women;this is similar to the fact that most gay men may penetrate gay men but will not penetrate women although at some time in the past they may have experimented. Of course their are exceptions.
Pick a ts who is into penetration, if this is what you want, in that case a ts who is not on hormones, this may give you what you needm a good stiff one--just get on the phone and tell them what you need and that your are willing to pay for it, or frequent a ts bar and a finger on a thigh will get you a quick answer, chances are you will get filled and fulfilled eventually. Try to find a ts who is enthusiastic about the idea so it is not a work load.
I would not look for a threesome as one suggested, instead give it all your attention and see if this is what you are looking for...by the way, you might be prepared beforehand to receive anal intercourse as this may be preferred, but you might discuss this before hand. Oh yes, I hope you know how to suck cock, if not you can ask for lessons! Very few woman can give a blow job as well as a ts.