Don't go too cheap....
Sometimes you can find used ones on chocolate websites like 70%., but not often.
D & R (design and reaization) in Montreal carries the "Savvy" brand from France. Although this band is expensive, (I think around 2 big ones for the basic) it won't give you much grief. Cheaper ones have a plastic (nylon) base. Not good. Better ones have an aluminum base, Good. Better ones are a snap to take apart and clean, cheap ones aren't.
Ther are single cut and double cut guitars. Single are cheaper, and in my opinion,better. True, you have to move the slab you're cutting twice to get squares, but with a double cutter, if the base ever gets dropped or damaged, both frames will rub against the base and the wires will snap.
The cutters are only good for ganaches, pate de fruits, petit fours--anything soft. No-go with hard candy, caramel, anything with nuts or candied fruit pieces
I still haven't got one yet. It's on my "wish list", but I make do. I buy pizza cutters with a 4" wheel for 2 and a half bucks--by the dozen-- and pop out the wheels. I make some handles and some spacers,and thread it through a length of 1/2" all-thread rod, s/s acorrn nuts at either end complete the job. If I pop this contraption in the oven for a minute or two, it cuts like a knife through butter--or ganache....
Hope this helps