Try the Panasonic ER224S Cordless Hair and Beard Trimmer. It's inexpensive and works great! Stays charged for a long time and cuts from about 1/32 to 13/16 in 14 increments. The head slides to corresponding settings and locks when the unit is switched on. Cutting the back and sides of back requires one stationary mirror and one like a mirrored medicine cabinet door, pretty much directly opposite on another. It's a bit tricky, but you can do it. Thing to keep in mind is begin cutting on one or two settings longer than you desired length--this will give you feel for the cutter and a better idea of just how short you want to go. Another thing to remember is if you cut it a bit too short, it will grow back. That does little to temper one's dismay when an 'Oh, no!' happens--a bit of hair-cutting empiricism being shared here.
Photo borrowed from Amazon.com -- my clipper purchased from same.