Just screw a bicycle's bottle cage to the rollcage... err i mean glovebox lid. :)

I think Ringle' still makes CNC billet-aluminum bottle cages in all manner of designed colors. Alternatively there ARE bottle cages that are designed to hold handled mugs.

Forget all that jury riggin', just do what I did and get a nice setup from Manntis, can't wait to get mine! Check it out
http://www.wigglepup.com/gear/feature_cupholders.php

I almost forgot, the first 50 people to order cupholder/radio rig gets some free RX-7.com Stickers!!
:D

My other car is a 89 toyota corolla and they have a small pull out two cup tray that I keep wondering if it would fit below the stereo if I move the stereo to the top of the din's I think there would still be a little room to shift but it would be very close.

*nudges mwpayne* Should let me know before you start giving away stuff on my behalf *L*