There's a scene in London Shaggers #1
Amber Sex aka Amber Angel (she goes by
Amber Sex in the scene)
Shes riding the guy reverse cowgirl. I dont know if its intentional or not because he does pop out a few times, but he pops out, and she quickly re inserts him, and you can clearly see he had started to blow his load. A quick google search will locate the Scene "London shaggers
Amber Sex" second link (spankwire) is the correct scene. good part starts at 18:30
there's also a good flick that can be found googling "SHE SHOVES MY COCK INSIDE HER PUSSY AS I START TO CUM" PoV no faces good part starts at 6:33
hope this is what you've been looking for.