I actually just put it in the cup holder its self, I have a nylon carrying case for the 100. I also use a Larsen tri-band on my car and hook it up to the coax while it sits in the cup holder. If you're going to use the antenna on the radio you might want to get it higher and proclip, just look it up has great holders that snap into your vent and you can use the belt clip and it brings the antenna above the body of the car.
For a while I used as seen on TV cup holder that screwed into and tightened on the cup holder of the car and then it was a phone mount type deal. It held pretty tight even with the coax attached but it wasn't long before it just fell apart LOL.