Bergara Action Barrel Replacement

Off the top of my head, Preferred Barrel Blanks, Urban Rifleman, and Outlier will happily sell you a barrel-nut-style, adjustable-headspace barrel cut specifically for the Bergara action tenon and bolt face geometry. You'll need headspace gauges, an action wrench, a barrel vise, and possibly a barrel nut (sometimes sold separately) to complete the job. Depending on what stock you have and the contour of the new nut-and-barrel combination, some inletting may be required.

Plenty of other gunsmiths (including PVA) will machine a blank, either one you provide or one you buy from that gunsmith, to fit your action if you can send it in and wait however long they need, usually a few months.

What are you trying to accomplish with the barrel swap, though? Are you currently having issues, shot out the factory barrel, looking to change chambering, etc? By the time you add up the treasure, time and tooling to swap tubes on a Bergara, you may be well over 80% of the way to a nicer barreled action.