http://www.hcb-autotools.com/component/page,shop.product_details/category_id,18/flypage,shop.flypage/product_id,961/option,com_virtuemart/Itemid,1/vmcchk,1/
http://www.austools.com.au/fuel-system/universal-adjustable-fuel-tank-lid-remover-/-installer/prod_1210.html
This also looks like it might do the job:
http://www.austools.com.au/fuel-system/electric-fuel-pump-fuel-tank-retaining-ring-adjustable-removal-tool/prod_113.html