Found an example of those kick-ass cupholders on ebay http://img.auctiva.com/imgdata/2/5/4/8/8/7/webimg/34346269_o.jpg Kind of pricey, but it gives you an idea and a part number if interested. A trip to the local wrecking yard with a sawzall might be cheaper and a lot more gratifying cutting a "luxury" automobile dash to ribbons. http://cgi.ebay.com/ebaymotors/Saab-9-5-9-5-9-5-OEM-Dash-Mounted-Cup-holder-99-04_W0QQcmdZViewItemQQcategoryZ63691QQhashZitem230099938009QQitemZ230099938009QQrdZ1QQsspagenameZWDVW
I like the ideas of a connecting rod or finned oil filter housing that would swing back into or under the dash.
Look to boats for inspiration. They use holders that swivel to stay upright: Or this: Maybe this would look good in the center console of your custom: I tried searching for a photo of the old 1950s underdash bar dispenser units. I forget what they were called, but it allowed you to make mixed drinks from the dash of your car -- available from Almquist, Pep Boys, and similar accessory places.
Man I haven't posted here in a long time. But I felt I should weigh in with my vast cupholder experience. The Saab ones suck. My wife had a 9-3, maybe like a 2002. The cupholder is too weak to hold anything but a half empty Coke can. Too much splashing and such. Seems like it's gonna break off. Not to mention your drink splashed on the CD player. I like the wire swinging boat ones. I pulled some out of the U-Pull-It yard at 8 and Hoover in Detroit. They have boats and motorcycles occasionally. That must have been a $2 investment. Plus they're very patina-rich. That said, the wire VW one is really nice too. I have one, bought from cip1.com for like $20. Comes in chrome and maybe black and white. Looks old, and suits the purpose very nicely. You gotta check out that sight for tons of cheap bits and bobbles.
Thanks for the input on the SAAB ones airkooled. This is good information to find out before springing for a set - because I like the design engineering so much, I might have to make my own set out of scavenged metal. I would feel less streetrodder that way.
Here's a necessary matching accessory: http://www.banaire.com/relieftube.html Every hotrod should have one.