You know its not actually a cup holder (of course), but when Im traveling in Marlin's 80, I can stash a 32oz or larger cup to the left of me, between the seat and the door. He has bench seats and his seat is narrow at the back and then get wider as they move out. So I've found that, for instance, large Taco-Smell cups fit perfectly in that narrow area and up against the door. Just remember to hold the cup when you open the door.
As for cup holders, You could always go with the old fashion Jeep/Landcruiser aftermarket cup holders... I used to see them out on the trail because the dash on a LC is flat and its easy to mount.. hang on let me find a pic....
Ok, here's a modern example of this style:
In fact, check out that page where I found that pic, its here:
Gadget and Attaching ComponentsMaybe you could rig something up
BigMike
