The plastic power button on my Edge 1000 became brittle, and fell apart. Seems a common issue with Edge 1000. I contacted Garmin, they wanted £195 in UK to replace with a 'refurb', or 30% discount on a new Garmin. My Edge 1000 was fully operational, did not feel £195 to replace a piece of plastic was reasonable.
I see a few options online to repair, using 3D printer etc, but I had a look around and found a small tie wrap & electrical tape can be used for a simple repair.
1) Find a suitable small tie wrap
2) Carefully cut out any loose plastic from the original button
3) Cut the tie wrap, and put a piece in, and trim to its flat on one side and slight nipple on the other
4) Align the nipple with the power button and test
5) Apply some electrical tape to keep in place and keep water tight
I have also ordered a silicon case from eBay for a few quid, to hide the repair.
HTH!