I thought I'd do some snooping around for you. Since I don't have an infinite amount of time, this is all I could come up with right now.
You asked for an escort service, I know, but I'm more familiar with the BDSM scene. However, some Houses of Domination also accommodate tickling sessions. If you are the tickler, then chances are they would consider this type of session a "submissive" session. Therefore, the rate will go up. They may or may not do outcalls. You must state what you are looking for up front.