Is this possible?

I recently got a topeak ridecase for my iphone 5s and it's a great system, but requires a threadless stem cap to install the mount the cleanest way (otherwise it has a handlebar mount adapter)



As you can see it replaces the stem cap and bolt - works great on my rumblefish but not so much on my `84 road bike which is the bike I intend to use this with the most on long rides so I don't have to pull over and stop to pull my phone out when I get lost

I've seen the profile designs and origin8 adapters but it looks like the bolt system for them goes through a permanently attached stem cap?

Any ideas?