Ring Restock for Vendors in Ward 13?

[Veezora]

Currently I have been playing as Engineer, and I'm aiming to get the Mechanic's Cog ring. The wiki says it appears in Cass's shop, although my friend found it in Reggie's. Either way, the selection of rings being offered never changes, even if materials and consumables restock. Is there a way to get different rings to appear in the shop, or do I just have to join games and hope other player's vendors offer it?
This is on a nearly-completed campaign.

[dr46onfusion]

It's RNG and Cass seems to get rings at certain periods of your campaign progress oddly.
Her restock is mostly for materials, maybe her 'rings' and assort of non-material items is based on real time days?

[Jeff]

I'd re-check cass' inventory after each major event boss.

I'm on my second story playthrough on teh same character and completely different rings are showing up. Feels kinda random but I'm buying them all just in case, and new ones keep showing up.

FIrst playthrough seemed to have fewer but maybe I wasn't checking as often.

[Caperook]

Every restock happens once in 30 real-time minutes. I got both the Cog and the Amber Stone for the Archon randomly.

There is also a trick to force vendors to restock: go into any world, change your system time (yes, system time - Winows clock) - add 30 minutes, then warp back to Ward 13. Vendors will restock.

Getting the Cog that way still took me around 10 trips, and another 20-ish for the Amber ring.