I've got a TomTom "beanbag" mount. OK, but only if you've got a flat dash top - worked OK-ish in the 147. Garmin used to do a better one, which had flexible attachments for the weighted bits, so it could conform to the shape of the dash, but the only one they list now has a specific Garmin mounting rather than a flat area which uses the suction mount.
I used to have a bm 3 series with a tape deck.
A very handy piece of plastic I cut to shape and slid it into the hole with the satnav mounted on that, made it easy to use as the windscreen was miles away, and the *** lighter was handy too....I'll see if I can find a pic...
I've got the Garmin "bean bag" mount. I position it to the right of the rev counter on the dash. After several attempts I now stop it falling off using a 19mm (25mm will also do) fold-back type of paper clip - clipped to the air vent (the one that aims air onto the side window. It works a treat!