You really can’t go wrong with a Garmin. The 795 is a good model, but really any of their RV GPS models are good. I don’t think any GPS is perfect as far as routing, but the RV specific features make them invaluable. Downside, they aren’t cheap. The 795 currently runs around $400. Here’s the model I have on Amazon.
I’d also recommend carrying a Rand McNally Motor Carriers’ Road Atlas since it’ll never lose signal.