I know it's a different fob, but I got new replacement cases from Ebay for my Disco II. They also included uncut keys, and changing out the guts was a snap. So, I imagine that those tricky Asians also make one for your application.
'99 Disco II
'76 Series III Hybrid 109
'95 R.R.C. Lwb (Gone...)
'70 Rover 3500S (Gone...)