I think you have pretty much answered your question:
I ordered a bag of belts and matched them up pretty close
I found the Teac part #'s "Full Auto Belt" #9278246200, and "Main Belt" #9278247200. I cannot find these cross referenced to a size description, so it could be ordered. They are both flat rubber belts, and I am sure they can be sourced, but we need dimensions.
Be sure you removed all belt residue from pulleys, etc. There should be nothing but shiny surfaces for new belts. It's tedious, but you might swap some different ones into the deck-from your assortment. Perhaps tension is low-so use a shorter one-but don't go too far with tension. That will strain parts over time. Many aftermarket belts are too thick-see if you have any thinner options among your supply.
There is the string measure method as well. Take a string, and use it to go around the pulleys as the belt would. Measure this length. Measure the width of the pulley. Choose a belt that is the same or slightly shorter than the string, and is about 80% of the pulley width. This should give you a decent shot at getting a useable belt.
Search for Russell Industries, and get their PDF Belt Cross Reference. Near the bottom, you will see the belt sizes. You want the FR series (flat rubber belt). Get the one that is closest in circumference, and width. (IC=string length, C\S=belt width, Wall=thickness) If a thinner option for the same IC and C\S dimensions is available, choose that one.
Then you need to call Russel to purchase the belt(s), using their FRB #
