Need Make & Part # for R-29 (Classic) Shower Mixer Valve/Cartridge

[Sea Spirit]

Greetings again from Sea Spirit. Much to my crew's dismay, we discovered the shower aboard our 2013 Ranger Tug R-29 (Classic) dispenses only scalding hot water--no cold water mixes in at all. The nearby head faucet and the one in the galley work just fine, dispensing water whose temperature we can easily control. The former owner told me he had never used the shower during the 5 years he owned the vessel. I've accessed the valve itself and turned the setting screw as a test--turning cold-side screw resulted in no change (still just scalding hot water), and turning the hot-side screw shut water off completely to the shower. So we suspect a faulty cartridge within the valve, or perhaps the entire valve assembly is faulty.

Can anyone tell me what make and model number was used in the 2013 Ranger Tug R-29 (Classic) shower valve mixer and/or valve mixer cartridge? At this point I'd settle for replacing the whole doggone valve assembly to get the shower operable again, so if anyone's been down this rabbit hole before and found a solution that worked, I would be very grateful to know it.

Attached are photos taken of Sea Spirit's shower valve and cartridge.