Can't recommend a transfer switch but will point out an alternative. My trailer has a receptacle hard wired to the generator. I plug the shore power cord into the receptacle when I use generator power. Simple, low tech, and low cost.
Build a life you don't need a vacation from.
2016 Silverado 3500HD DRW D/A 4x4
2018 Keystone Cougar 26RBS
2006 Weekend Warrior FK1900