Sorry, I'm going off-topic!
I think if you get the belts and install them yourself, it would be way more cost effective than the other route you're heading.
PLUS, there is a subtle and little known difference in the head configuration between the 246 and later models. Specifically, and adjacent-track phase reversal,... which was a unique head design to early Tascams that reduced or prevented crosstalk,... and it worked superbly well,... but they abandoned that head design to be a more "compatible with everything" type of unit, in later Porta's. THE REAL MEAT AND POTATOES of that head difference with later models will be TRANSPARENT,... UNLESS you did some 2-track simultaneous stereo recording to the 4-track on the 246, on which upon later models would give you AN UNFORGIVABLE PHASE CANCELLATION. Heed my words, my friend.
Anyway, IMO the 246 belts should be $15 or less, and are easy to install by a monkey with a screwdriver, so would be your best bet and way to go.
NOT ONLY THAT, but the 246 mixer, component and sound quality is MILES ahead of the later Portas.
Just sayin'.
Okay, then,... good luck!