Believe it or not, such videos do exist. Ticklehorror.com has at least one where a guy watches his gf get tickled while topless. Realtickling had, or might still have, a two-parter where Kristin Lea is saran wrapped to a board and got the crap tickled out of her while some guy sat in the background reading a magazine. I'm guessing he was her fiance, because I read somewhere on this forum that she retired after getting married, and that was the last video I remember seeing her in. James Darke has a thread on here listing certain models who brought their significant others in to watch while they got tickled. I don't have the exact links for these, but I hope it points you in the right direction. Good luck!