There is a “frame and axle shop” near me that custom builds leaf packs. They typically work on fire trucks and large rigs but they did my alignment on a previous toyota camper. 

I think if you load your sunrader up with a weight you’d expect it to be when loaded up and then go have it weighed, you’ll get a front and rear axle weight. Take that number with you to a shop that builds leafs as well as your old leaf pack and they may be able to custom build you a pack. 

Anyone?

Should be able to find the factory specs and get a leaf pack from most anywhere that sells springs or a lift kit company. Also just measure the shocks and get some good aftermarket ones.