How to find a girl for my girlfriend?

Hi everyone,

This may not be a typical question but my girlfriend has this fantasy that I would watch her having a massage / sex with another woman.

That woman could be from a paid service but she has concerns that this may bring health / hygiene problems to her. On the other hand, to find a woman that would do it without a payment being involved may be challenging.

So the question is: where / how would you search for a girl to satisfy this fantasy? Do you have any recommendations or suggestions?

Thank you