Impossible to find Shower Cartridge?? Help please!

[Kidmag]

Our plummer said our shower cartridge is impossible to find and we need to just replace our whole system. We love our fixtures and obviously for many reasons (not the least is $$) would much prefer to just find the correct / matching shower cartridge. I'm hoping someone here will have seen this cartridge before and can provide any assistance in sourcing one. Thank you!

I've attempted to put two pictures below.

 

[Smooky]

You need to shut the water off. Take the handle off and remove the cartridge. Take infocus pictures from the side and both ends of the cartridge.