Need help finding parts number for Sanyo Betacord Idler Tires.

[VintageLove]

I recently contacted studiosoundelectronics inquiring about idler tires for my Sanyo Beta cord 7200.

Unfortunately they only sell the belts and idler tires are no longer being manufactured.

I found a website called http://www.electronicsupplycorp.com/.../en-us/d9.html

They do have several but i am not exactly sure what parts number i need.

I'd greatly appreciate anyone who can help me out here