Chosen Solution
Where can I buy the 2 plastic sliders next to the mouse cover?
Sorry, not a replaceable part. Review this IFIXIT teardown: Magic Mouse Teardown. If you can find a junker to swap out the part thats the only way.
The black plastic rails are not needed. Mine kept falling off my Apple Magic Mouse, so I eventually just left the rails off. Surprisingly, the aluminum bottom of them mouse slides fine over a cloth mouse pad and works fine. The rail-free mouse also works okay on my table; however, it makes a light scratching sound when I use it on a hard surface without the mouse pad.
