I couldn't find a Garmin mount for my Etrex 30x that fitted where I like it on my stem. As the stem is fairly short I found the garmin slide-in mount was catching on the stem spacers. I saw something on a USA website but couldn't justify the cost in shipping it over.
I used to have an Edge so I cut the lugs off the twist mount adaptor that I had for that and used black Sugru to glue it to a spare slide in mount. This mount was very tight initially so I had to ease the 'runners' on the mount to make it easier to slide on and off to get to the battery compartment on the unit itself.
It is easy to twist on and off the mount on the stem with the slide-in mount and sugru'd adaptor staying on the unit unless I need access to the batteries.
Not overly pretty but a fun evening spent getting something just how you like it!