Wanted: 13” rear shock, what model should I be looking for?

[thefox]

I am looking for a cheap shock that is about 13” from center of mounting bolt to center of mounting bolt. I am making rear suspension kits for the Yamaha YTM200, YT125 and YT175 3 wheelers and need a shock. It will be a non-linkage setup, I am attaching a picture of want I am basing my design (heavily) on. Any help? If you have a machine with a rear shock, please go measure it and post up if it will work or not.

http://i259.photobucket.com/albums/hh293/thefoxman45/PICT0026.jpg

[85200xrider]

i dont know if i am measuring right but it looks like my 200x rear shock is just about 13"