well if the remote works fine other than the rubber being worn, your best bet is probably to buy a replacement remote from fleabay (with or without the key) and swap the casing over (ie transfer the circuit board inside your remote to the new one), then re-fix to your original key ... no reprogramming required !!
be aware that there are three types (as I found out) - the older "megamos" ones - it may say this on the back of the remote if it hasn't worn off, otherwise it is printed on the circuit board, just below the battery. The later delphi ones generally do still show "delphi" on the back, but be aware if you like the light when you press the button, that some of the delphi ones don't have a light (or a hole for one to shine through) ...
Right an update, I have fixed BOTH my remotes full reconditioned and here's how :
2 x new remote units from ebay £11 each reccomend seller (these were the newer delphi one, mine were older megamos)
I dismantled the new remotes and carefull de soldered the 3 click buttons on the circuit boards
did the same to my old remotes (you have to remove the LED on the board to be able to solder the new buttons on)
solder the new push buttons from new unit's on to old circuts (my buttons inside had failed)
reinstall the old board into the new case's with new batterys and new switch's (all you really keep out of old electrical unit is the already programed circuit board !)
and there you will have a fully reconed remote unit !
I have left over, 2 x empty shells poor condtioned rubbers but good plastic's
and 3 useable internal switch's if any one needs any let me know