Southpaw here.
Not finding many choices for LH draw.
Would like a factory model similar to SW 21-34.
Any ideas?

Also a lefty. Don't happen to know offhand many model numbers of various makers from times past. As you suspect, information might be found by a search using "Holster charts K frame Smith & Wesson 6 inch barrel". From my own small stash for K Target 6", the Bianchi Cuclone 111 cross draw for S &W/Ruger 357 is a good fit. Less heavy duty is an old Hunter 1100 15 - unlined with straight drop. Both are closed toe.

Many of us have had good luck prowling at gun shops, gun shows, searching eBay and, far less productively, just waiting for one to pop up. You could also try calling, say, Galco to inquire if their Outdoorsman, ~similar to the model you mentioned, would be available in LH, the color you want, 6 inch barrel and your preferred cant.

All best.

I am also a lefty and have my saddle shop make my holsters.
They have a guy and ALL he does is make holsters. I have posted them here before. Send me PM is you want more info.

__________________
V/r,
Markham

If you're looking for vintage leather, try doing an Ebay search using the word "vintage." I see LH holsters by the score on there all the time.
Also try Forum member "Robbt" 's entry in the misc for sale sub-thread. It's a bit disjointed, but you will find some lefty gear and he doesn't charge an arm and a leg.