So... my SatNav is a rather venerable TomTom One. I've had it so long because it "does the job it says on the tin". It must have paid for itself many times over in petrol savings. The one thing I do not like about it however is the terrible window suction cup, which, no matter how much spittle and slobber one applies, likes to celebrate life by dropping off on unfamilar five lane, close your eyes and pray, roundabouts.
I bought a bracket on ebay which clips into car vent slots - fits most types of car it said - but not my car, a clapped out Vaxhaul Astra. So then I discovered that they do "Bean Bag Dashboard Mounts". It's a bean bag, with a bit of plastic attached, and they want... 25 quid for it. HOW MUCH? I'm not paying that! (Well belatedly I discover that there are unbranded copies available for half that. Too late now..)
So I made one for free. Yes, genuinely, all parts and materials were things I had around the house.
I used: The original suction cup and connector, an old Wallace and Gromit sock (any old sock would have done, but Wallace and Gromit seemed appropriate for an Instructable); duct tape (some chaps who did a fencing job for me left it behind, they charged me a king's ransom, so I did not feel too guilty about the gain); a piece of hardboard (the white kite shape on it in the image is the legacy of a previous use, and before that it was probably a picture frame backing); wood glue (strong PVA); a piece of non-slip matting (it was left over from a length I bought to sit under a scroll saw); a handful of gravel (from the greenhouse for top dressing potted plants); a piece of plastic coated garden wire.
I started by making a base. It had to be as large as possible for stability, but then no bigger than what would fit on the dashboard of my car, which though level, has dipped pockets in it, and no bigger than what would fit into a sock - and it was a really old thin threadbare sock. I tried a drinks coaster intitially, but it looked like it was going to rip the sock, so I cut a piece of thin hardboard to a slightly smaller square. I popped off the corners to get it into the sock without snagging.