Along with trying this post on the Vegas board, there are proactive ways to find reviews of ladies who might be into it.

You can restrict a search, under "2 girl action," to girls who are "really bi" and, to avoid dead ends, restrict sex to "yes" (you might as well do that for any search unless you are specifically looking for just a massage and happy ending).  I just did a search like that for Las Vegas and got 389 hits.

There are many ways to limit searches and zero in.

When I repeated the search and restricted it to white girls, 25 and under, with natural breasts and average ratings of 9 or 10, I got 8 hits.  Seven were last updated less than a year ago.

I'm gonna go out on a limb and say that one of those ladies would join you and that you'd have a good time.  Don't know you, don't know them, but that seems like about the safest bet you could make in Vegas.