I actually have a really cool black anodized cupholder in my 73 targa for those solitary weekend mornings with just me and my double latte.....
Bought it from a company called JM Products Design, whose website does not seem to be working today...not sure what that means.
Anyway - it WORKS!!! It will hold anything, has a moveable top rail AND a bungee cord attached, comes in black and some hot colors, is about $19.95 and is of good quality, and easily removeable, etc..
No affiliation, just a customer
YMMV,