For my Fascinate I found a very similar mount on ebay (for another Samsung Galaxy S model on another carrier) and then spent a minute with a dremel making it about 2mm wider and it works great. It's not very low profile (it sticks up a ways) but I've taken it for trail rides on my mtn bike and never had an issue).

http://www.ebay.com/itm/Bike-Bicycle...item3cbc3389a5

It may take you a few minutes of looking around on ebay for a mount that is really close to your phone (go for slightly smaller if not exactly the same dimensions).

Before I bought that mount and made it work I would take my armband and wrap it around my stem a few times before securing it with the velcro. That worked pretty well too but having the thin clear cover over the screen was annoying when I wanted to access the phone when stopped...never really tried it while riding...on the bike mount one the screen isn't protected.