In a gen1 (and somehow, in everything else I drive), I use an old QuikTrip 34oz biggulp drink holder that was made with a biggulp wide x approx3" deep flange on one side to slip into the gap between seat cushion and seat back, with a 1/4"lip on the end of the flange. Flange makes more than a 90* angle by 10* or so to tilt the holer on the flange to "match" the seat cushion slope. In the gen1, I whango'ed the flange into the gap between the dash center lower console and the shifter. The flange broke off the holder years ago from the leverage a full cup of 34oz of Kona put on the plastic, but a sheet of 1/8"plwood fixed that.

In the gen2, the cupholder goes with the flange under the edge of the front seat, cup under/to the right of right knee. Not ideal.