I have got a PAQUAmobile it fits on my arm and has never come off even on a nasty harness flick or two.
www.paqua.com.au (The music is terrible)

It has an overlock on the armband, I can turn the NAVI on or off and I haven't had to protect the main button as the cover bows out around the GPS.

Cost $29.95

I was using a an Aquapak but have found this to be much better.

My 2c

Whitworth Marine, 634 Stirling H'way Mosman Park - good selection of both Aqua Packs and PAQUA gear.

They also have a store in Leederville, never been in that one.

T

thanks graceman.

looks like they sell those paqua's at most good outdoor shops etc as well.
cool.