You can also call Metrics Unlimited. Their plug is very popular and very well made too.
1-800-638-7986 between 9:00 am and 3:00 pm EST M-F, You will need to know whether it is a 5/8" or 7/8" breech plug. The cost is around 35 bucks shipped to your door/mailbox , I'd ask for Bob who can help you out or direct you to someone who can