Finally, after almost a year of searching and pondering, I've found a solution for the cupholder issue.
First, here's pics:
XM tuner, followed by the cupholder in the closed position.
XM tuner, followed by the cupholder in the open position. It has a spring-actuated lip to adjust to different sizes. Also, it has a drip tray underneath to avoid spillage.
Next, I'm going to order two for the back seat arm rest.
Cost: $17 Shipped USPS Priority, available at ultimatecupholders.com. Called the "Fischer" folding cupholder. You can also get it on ebay for $16 shipped.
The plastic feels surprisingly durable, and you can have it mount to a horizontal or vertical surface.
3M extra strength double sided mounting tape is what I used to mount my XM tuner and cupholder. The cupholder came with rails and screws but I wasn't interested in drilling. $3 at Wal-Mart for a small roll. It holds surprisingly well, and removes cleanly.
-Jesda
