Not sure if it fits but its $15

https://www.emf-company.com/store/pc/-2-1873-GWII-Cylinder-Base-Pin-p1759.htm

Numrich has the uberti, for $23 … made for the 1873 cattleman BP”
But, having several of those I can attest that the parts are interchangeable with the cartridge 1873 SA

https://www.gunpartscorp.com/products/2042930

And if one needs video halp with a diy here ya go



Yhs
Prof mumbles

Many thanks for all the thoughtful recommendations.  I've checked every recommended source and all were either out of stock or thought their products worth $40 a piece. My inclination at this point is to go ahead and grind one back and go from there.  I figure if I fail, I can always backorder a replacement. 

I totally agree.  I tried to talk the owner out of the bastard-child with the park job, but he was fond of it.

  Lou 

That Rifle be Right Yummy you betcha.  GREAT find 

If you don't want to cut or grind off a little of the rear of the pin, you can replace it with a Colt base pin (pricey) or just order a standard length Uberti pin (this is what goes into all the new Ubertis the last half-dozen years.  When they came up with their retractable firing pin safety design it eliminated the need for the two-position base pins).  VTIgunparts.com or Cimarron or Taylors or Dixie.