"... he said it wasn't the CV joints but unsure what was producing the sound..."
Is there another dealer nearby to get a second opinion? The tech might be right but if it's warranty work anyway a second set of eyes may be worth it.
Years ago I had a '79 4x4 Suburban with 350 4bbl, auto. The thing would shake and resonate around 70 mph. I replaced tires, rims, front and rear hubs, and still it shook. So I had custom front and rear drive shafts made (spund balanced to something like 35,000 rpm). Still not right. So I had all rubber attach points in the front and rear suspension replaced. I was going to find this "problem". nope, still hsakes. So pulled the motor and had it balanced and blue-printed and breathed on real heavy (cam, crank, pistons, hi flo heads, solid rockers, etc.). While the motor was out I had all exhaust attach points replaced and new pipe and hangers put on. Geez, I'm already this far in might as well get the tranny done by the local speed shop including new torque converter, B&M shift kit, and new swash plate.
After all of that work the thing ran at eye watering speeds and got there quickly ... but STILL viberated. Close to 25K$ spent chasing a "problem" and in the end I still had a '79 Suburban with rust, dents, and pitted chrome worth nowhere near what I spent to "fix" it.
Next time I'll either live with it or sell it and try again with something else.
So to answer your question, I don't know of any custom or heavy duty U-joints for these trucks.
Box Stock: 2011 White Gold Ram 1500 SLT CrewCab - 4x4 - 5.7 Hemi - 3.92 LSD - Integrated Trailer Brake
Cabin Air Filter
Cooper AT3 tires
Mopar Chrome Lower Body Moldings,
Mopar Fog Lights,
Mopar front & rear Skid Plates,
Leer 180 Cap w/Wilderness Package,
Rage roof mounted Cargo Basket
Weathertech over the hump floor mats
Clazzio Leather seat covers