Alternator gasket

[Falcoholic]

Where's the best place to get a replacement?

Mine has been off a couple or three times now and should really be replaced but I dunno where to get a new one.

Any ideas?

[D-Rider]

One of the Aprilia dealers I guess ...........

Not sure if you've got one local - if not plenty do mail order .... and I'm sure Griff would sort you out:
http://www.apriliaperformance.co.uk/Main/main.html

[redfalco]

I got my last one from inmoto, got it in the post the next day.

Changing the bolts is a good idea whilst your at it, I managed to snap one with very little effort.