Consider an air ride seat. There are several threads here saying good things about it. I don't have experience with it though.
If you have a loader, maybe you can get an hydraulic accumulator that absorbs the shock during loader work and just driving around.
The smallest tractor with front suspension I can think of is around 75 HP over here in Europe but mostly are for Orchard and vineyard. Fendt, Class, Deutz are a couple of them that offer front axle suspension. Although the price rises rather quickly.
I've thought about this several times. It would really nice if someone would make a compact tractor (35-60HP) with front suspension.