Four Lifeline GPL31XT AGM batteries which are 12V 125AH and 76 pounds each would give you 6000 watt-hr maximum, 3000 watt-hr useable at 50% drain 1000 cycles, 304 pounds.
If you could be happy with 500 cycles you could get 4200 watt-hr out of them according to Lifeline cycle specs.
Cost is about $1500 with free shipping from powerstride.
50 cycles a year would be using your camper about 5 to 10 times a year which probably is well above average. After 10 years there will probably be a newer better tech.
