I think the cheapest and fastest bet would be to go to a hardware store and purchase a rubber pipe washer.
I have loads for Marty. Whether they are the same or not I can't say. If I remember I'll pm you when I get home.
The correct answer is "no". You earn 5 points for a creative answer. If a rubber band was all that was needed my circa 1950s reel to reel player wouldn't be stretching out every tape played on it.
Thanks dude. It says in the title "FM Towns" but i do actually need a marty belt. I was actually hoping it would be you that would see this message as when i was googling about it i noticed you helped out someone back in 2006 or 2007 that had the same problem on here. I thought about getting one from a Famicom disk system but i think you mentioned they are too big.