If you don't mind shooting dollar a round ammo, you can get some at the odd gun show.
In all honesty, if I happened upon one of the 5mm Remingtons these days, it would rapidly end up re-barreled into something I could buy without a mortgage. Maybe a .17HMR, maybe .22WMR.
Or consider a centerfire conversion. Lots of the guys that had them, went that way. The action is plenty strong, but it does need to be threaded and a new forward section made for the bolt. There are some details available on the Calhoon website, if you are interested in looking.
There was some talk of someone having picked up the Aquila distributorship, but I have not seen or heard anything of substance. Watching the NRC list of approved ammo for the stuff, is about the only way I figure a guy can stay up to date for sure.
Mostly, though, I think you are pretty much outta luck. The odd lot shows up on the EE, some at gun shows, none on the shelves. Or you may get lucky and be contacted by someone with some to sell.
Good luck!
Cheers
Trev