The P2 has a typical problem where the buttons tend to wear down after several months of use. So I'm sharing again how I fixed mine. The replacement buttons have so far been more durable than the original although it isn't as soft.
1. Get your copy of the 3D plan - Google 'pebble2 side cover by Yusukeyusuke'. Click the thingverse link where you can download the necessary files.
2. Print your mould - Send the thingverse files to your 3D printing supplier (if you don't have a 3D printer). I had mine printed by a supplier I found at 3D Hubs. My mould was made of ABS plastic. Try to get the most detailed print possible.
3. Create your buttons - I used 2 packs of Sugru, first to create the button, the other to attach the buttons to the watch. It takes 24 hours for the button to form.
Before putting Sugru on the mould, place a 'release agent' on the mould's surface to make sure that the Sugru doesn't stick when you remove it. The manufacturer suggests using cling wrap or petroleum jelly. But what worked for me was spray on butter you use for baking.
4. Attach the buttons - I like to put a thin layer of Sugru on the corners of the watch and then place the button on it. Keep in mind that your watch probably won't be waterproof anymore after this procedure.
Hope that helps!