Hi Ian, not sure how big the hole in your back panel will be, once you've removed your existing filler, but take a look here for an alternative type-

https://www.europaspares.com/10/FUEL_CAPS_and_HOSE.html

http://www.holden.co.uk/displayproducts....uel+Filler+Caps

Best of luck, Gerry.

Gerry