I love my NEF!

When you send it in to get a barrel fitted, you can request a trigger job for free too.

You won't find "magnum" barrells for the NEF. (I don't care, anyway.)

You can pick up some cheaper barrels on ebay(especially shotgun barrels). They might fit, and if they don't, 'do it yourself' methods are on the net, and they look pretty easy. If that makes you nervous, a gun smith could do it pretty inexpensively.