If you use xlights as your scheduler you can get by with an old old laptop. I've been using a gateway arc200, which is about 10 years old at this point. It runs on the old intel centrino chipset. I would think you should be able to pick something like that up for under $100 dollars. If you could find a good battery for it and set it up to run with the lid closed and the display off, you could probably make 6 hours...