Since your inbred plumber doesn't know how, call around to hardware and plumbing supply houses to ask if they have catalog to match cartridges and order if not in stock.

You will have to remove and take cartridge in to get it matched. Possibly have to reinstall and live with it until replacement arrives ( most shops have it shipped to you.)

klem1: Exactly how is your response helpful? You don't know that the OP has consulted a plumber. My guess is probably not.

This is a place where people who don't know can ask people who do. There is no reason to be rude or condescending. Every plumber I know is a professional, and absolutely none of them is inbred.

And, your advice is wrong! Are you even in the trades?

All the OP has to do is send these pics to Kallista customer service. Kallista does not publish a customer service email, but will be happy to provide one by calling (888) 452-5547.

Once customer service has the pics, the fitting will be identified. Kallista has one- and five-year warranties on shower valves, so most likely the fitting is out of warranty, but you just never know, it might still be covered. .

StarCraft Custom Builders , read second sentence of original post then read second sentence of your post.

3rd grade level reading comprehension.