I have had the same problem in the past, mainly because I often removed the top plate of mine (you need to remove the covering for that).
I tried several kinds of double-sided adhesive tape, but it always went off at some point. The best solution I found is :
- remove the front coverings completely
- completely clean them and the metal camera parts under them with a tissue impregnated with a solvent (lighter fluid or something similar). Don't use too much, it shouldn't drip in the electronics. It is probably a good idea to remove the battery for this
- glue the coverings back in place with 5 or 6 very tiny point of cyanoacrylate glue (krazy glue or something similar).
The coverings can be removed again later if needed, and the glue won't leave much residue. It can be scratched off before you glue it back again.
Cameraleather coverings are probably a good idea (I have a griptac covering on my M2, they're really nice) as long as you don't need to open your camera.
You can also buy spare original coverings and adhesives there:
http://www.gedat-ersatzteile.de/de/epssearch.php
(select digital camera -> Suchen -> R-D1 digital camera -> Suchen -> ref. 132, 133, 134, 135)