I have looked at what I had and they were old but all were still working.
You will need an adult check for this one. I have one that still works from 3 years ago. Paid for one for a 2 year and that was 3 years ago? try this one (appeal56sooner)
http://www.bondagepics.net/bdsm/pony.../ponygirls.htm

I'm sorry this one is very compleat but it is more about the Women ryding there gay husbands
http://www.thehumanequine.com/

And this is a link for a site that starts in the middle of the gallery but you can nav from there

http://www.lochai.com/Humanpony/content/index.html

Good luck in your ponification