I had the original gas cap with a guage in it and it leaked bad. Replaced it and still had a leak. I don't have a leak anymore since I put on a cap from a Snapper engine the part number is 1-2515 or you can get the Oregon substitute part 07-308. Fits like a glove. Cost was just over $10.00 here in Tucson, AZ. Maybe you can order one online from down under.
Joe in Tucson, AZ