Replacement parts can sometimes be hard to find. The case on the m105 can be easily removed, and a replacement shell casing can be used to replace your damaged one. Check out this site here for a replacment.
Remove the protective flip lid of the device. Open lid and pull. There is two clips the will pop out.
Next remove the face plate. There is a tab at the top of the device that un clips allow you to remove the face plate
Remove the batteries by opening the battery compartment on the back of the device. Remove one battery at a time
Using a T-5 Torx screwdriver, remove all four screws on backside of device by turning counterclockwise. Screwdriver located here.
Once the four screws are removed, you are able to remove the back and front cover from the interior parts of the device.
This is what the case of the device should look like when compleated.
You can purchase a new shell here: Replacement Shell Palm m105