Like everyone else said, GRS are nice. If you really want to go with a bead setup, Mossberg CS would be the best bet to order a beaded 590 barrel. You could always swap out your barrel and mag tube with that from a 500. They'll fit, but that's kind of like buying a BMW and putting a Honda motor in it. It'll work, probably reliably, but why?
Either way, if you do decide to sell the barrel or swap out the mag tube and barrel, let me know. I've been trying to find a 590 GRS barrel and mag tube and keep running into the same issue as you, no one has them. Then again, I haven't called Mossberg yet either.