They're expensive, there's an Airflo one that's about £70. Or look on Fleabay for a anodised Chinese jobby.
If you're not using them loads, I'd go for a Okuma Airframe. Cheap as chips, ok drag and graphite so fairly salt water resistant (always rinse).
In my experience they are finicky feeders and difficult to catch.
The best way to catch them and this is from the "Medway Mullet King." Paternoster bread flake on a small stout hook, using a bag of netted bread as a chum bag. With a quiver tip, something like an Avon type rod. I have not tried this method, but will do this coming Summer.
Bes