I'm pretty sure Onna of TGND does strap on even though I did not do it with her.  

I have done strap on in the past and it can be really hot.  Two pieces of advice:
1.  For a small amount of money you can get your own harness and dildo.  Sharing a dildo with other guys is way more dangerous than covered FS with an escort.  Even sharing the harness is as dangerous as the dildo going in and out will spread disease.  I'm amazed at guys willing to use public equipment - it's close to receiving anal from dozens of guys;
2.  Go small - see the link.  A bigger one may look more realistic, but a little goes a long way if you catch my drift.  And lots of lube.