Unfortunately, it's $20 wherever I look for a decent beanbag mount. Ridiculous! Garmin sells disk mounts for their products and many reputable dealers include dash mounts now. But what if you need a dashboard mount for your old GPS? Well it's pretty easy and cheap to make one.
Smooth, flat plastic or something surface (if it's not absolutely smooth, your suction cup won't mount to it!)
I used a cd case. You can use a jar lid.
Double sided mounting tape
Step 1: Get the appropriate materials
Obviously you'll want to try the suction mount before using the plastic.
Your scissors need to be pretty strong.
Ditto with the adhesive tape.
Step 2: Make the disks
Mark your circles on the side you won't be suctioning (the rougher side of the plastic).
I used a cup that happened to be slightly larger than my suction cup base (I could barely stick that sucker in the cup) with tape around the edges in order to mark my circles with my marker. Richer people can use that thing that helps you draw circles (protractor??)
Cut out your circles with scissors. Perfectionists can also file down the rough edges of the plastic.