Does anyone happen to know where this pic is from and whether there is more?

Here you go! It's on page 12 out of 18 for Nude Sport on the Vintage Erotica Forum website.

http://vintage-erotica-forum.com/t186533-p12-nude-sport-super-merged.html

Wow that was quick. Thanks! I was hoping there is a video somewhere...

You're welcome! I recognised the photo, & remembered where I'd seen it, so it wasn't so difficult to find again. Unfortunately, I've never seen a video, if one exists. Be nice if it did though