Try scavenging a rubber belt (the proper name) from a broken drive or find an electronics store that carries lots of small parts like that. That's the only way to fix it without incurring a cost that will end up being more than the cost of a new drive.
When it comes to electronics, you had best fix it yourself because if someone has to fix it for you, it's cheaper to just replace it. You're not going to find anyone who "fixes simple stuff like that" cheaply. It's all expensive.