You can buy special blanking screws for the mirror holes. I've seen them on ebay and most after market Triumph parts stores sell them. They're expensive for what they are, you might find bolts with the same thread in a DIY store.
The best way to remove the grip is to use a long thin screwdriver. Wet it with wd40 and carefully wriggle it along the inside of the grip. Then squirt a little down the sides of the screwdriver using the long nozzle and rotate until it loosens.
To replace - clean off all traces of WD40, spray the inside of the rubber grip with hair spray and replace. The hair spray will lube it long enough to be positioned and will set in a few minutes.
Last edited by denbow; 12-11-2012 at 10:19 AM.