I found these which don't require cutting the fairing:
http://cgi.ebay.co.uk/Triumph-Dayton...QQcmdZViewItem
110 though is a little on the expensive side for bungs, but if they work, then I wouldn't complain!
The others I was going to look at (other than GSG) are Sky king:
http://skykingproducts.com/Merchant2...Category=12874
General consensus on what I have read though is that GSG are the better design