Crate makes one for about $70 bucks. I have it; it's garbage. I play a 5 string, and those small amps wont give you good sound (at least in my experience). I suggest you buy a good amp. Maybe something with a 10'' or 12'' speaker. It will give you far better sound. (I'm assuming this is solely for practicing, not gigs?) Find a peavey or something; in the long run, you'll be glad you did.
