Any Plumbers Out There!? HELP!

[2LZ]

Hi all.....
As I've posted in the past....I've been helping out our friend who's husband 'untimely' passed away two years ago, with the log house I've posted pics of....and after the 'big' repairs to bring it back into shape, obviously, it's also been one thing after another in other smaller areas.....such as this. I get the call..... 8O

"Bill! I pulled out the knob to fill the tub for my granddaughter....and when I pushed it in....it wont work right! When my son messed with it, it came all the way out! Water going everywhere! He got it back together but it's about 30% shower/70% tub!" :x :(

I said...."Don't mess with it. It's working. I'll check it out..." :roll:

So, I went back up last weekend. It's a Moen (Moentrol) valve, installed in about 1960. Brass. Nice piece of work to handle her horrible 'well water' after all there years.
I've been to all the major box stores in Sacramento.... nothing. :( I've been to the Moen website and they don't have this valve listed anymore. :x All I need to do is repair the simple crossover between shower and tub. :?

There's one old "Mom and Pop they got everything" plumbing store I'm checking out tomorrow. Fingers crossed.......
If any of you'z guy'z are plumbers and know what this is....please point me in the right direction!
I don't want to have to tear the wall out, unsweat the entire assembly and install a new one! After all I'm no contractor but....it's not like her husband left her Trump Plaza just to "Call the Man."

Here's the culprit....


Here's the guts.....looks totally replaceable....if I can just find the parts.


Thanks for any input!