This is a punting forum for punters who pay for sex, not a voyeurism forum for viewing sex. Suggest you try spymania or one of the other amateur voyeurism forums out there.
We allow all sorts of paid-for sexual activity on this forum. Massage is not sex but it is included. If he wants to just watch, that is on the spectrum in my view.
OP, just book a MMF and let them get on with it. You pay half, he gets all the sex=win win. Or book a MF couple. If you were in my neck of the woods, you could watch my regular and me for a nice donation. Extra for her, savings for me.
Or attend a sex party. You are not required to fuck at them or anything.