I've seen the smallest ones available at places like MPJA and other "surplus electronics" places for $25 or so. If all you are interested in is just driving the RA motor so that stars sort of stay in view, they work great. The addition of the speed controls will make them a very cheap controller for those scopes that need to run on 120VAC. If your scope has a drive corrector already (it uses something other than the 120V60Hz syncronous motor) then you don't even have to worry about the frequency control. Even the 150W units will also drive a laptop or even a smaller regular computer. I haven't looked at the new flat panel displays but I suspect that they use a bit less power than a regular monitor.