If you are wanting a GPS simply as a backup then Garmin GPS Pilot III pilot is ideal. I use one for that purpose and bought it on e-bay for just over £200. It came in as new condition with various accessories and there nearly always appear to be ones on offer. I bought it to replace a Garmin 92 also bought on e-bay for just over £100. I was going to sell the 92 but give it to the short approaches to occupy them when they start feeling bored/sick.