Maybe try a custom builder, or a form 1. Ecco machine would do it, nicks cans are good but he’s a small operation. Liberty maybe would do it. There are quite a few custom shops.
I did end up finding 2 options, from the Cheytac thread. I just can't see myself spending north of $1500 on a single purpose can. The .375+ bore cans are aimed squarely @ a whole different market. I'm looking for more of a .375 SiCo Harvester style can for a hunting rifle.
I'm sorely tempted to roll my own. I'm pretty sure I can keep material cost under $400.
I have emailed Silencerco, and the Hybrid is rated for a 375 Ruger on I want to say an 18” barrel.
Now they didn’t claim hearing safe, but it had crossed my mind to reduce the blast on a bear rifle for being in Alaska. Not as effective as a dedicated 375 can, but another option.
SiCO Hybrid would be my choice. I use mine on a SBR 460SW encore, so I can't imagine a 375 Ruger rifle being any worse. I suppresses very well for the size of the can and such a high pressure round.
I dont know if it can handle that round or not, but maybe the bowers vers 45? Made for big bore AR rounds, a little more volume than the hybrid so maybe a little quieter. Worth an email to them if its something that looks good to you.