Yes they do have some bigger ones with screens and maps. Can you alternatively use your phone for maps? Etrex-like devices aren't that common any more.

Re prepaid phone minutes, they always expire and then your service is shut off / phone number cancelled, so you have to keep adding more. It's impossible to buy a 60 minute block just in case, and keep it unexpired if you don't use your phone. Everyone wants to sell monthly subscriptions so they can sit back and collect revenue while doing nothing.