You can order it: https://www.harmonyfarm.com/do.....l-1-quart/
I think I've seen it at Portland Nursery a few years ago.
There is another one you can get at Ace Hardware if you need a small amount. Many retailers have gone to gallon or larger size only.
John S
PDX OR
Sounds like pints are no longer offered. I'm not sure about quarts.
At the Fruit Propagation Fair, one of the vendors sells grafting seal for $14/pint in generic containers.
He doesn't label or advertise it as Doc Farwell's, but ...
He won't be at the Fall show, but should be back next March for future reference.
I find the best grafting sealer to break (cut) and share for the home or commercial orchard is the putty type, like molding clay. Once manufactured here in washington-Yakima, though not finding it, the same recipe seems to have shown up in Switzerland and I buy 1# blocks through OESCO in Conway, MA. they were $14 and it cuts up into 15 nice cubes, cost per cube?? $1
1 pound will seal about 1500 whip and tongue. I cut up ~1"x1"x1/2" cubes and wrap them in painters tape and send them along with scionwood if needed.
There must be a need for a ready-made grafting kit, complete! 
my 2 cents. oh, and the best pruning saw? after 40 years, same model...Silky F180 medium or fine bladed, fastest in the west. Competition?
Don’t know that I can justify purchasing another canister of Doc Farwell's, having my last solidify and go to waste.. Two days ago I dabbed the top cuts of 3 whip & tongue scions with an interior semi-gloss latex paint. The only difference I could detect was drying time; the paint took longer than the latex grafting sealer.
Viron said
Don’t know that I can justify purchasing another canister of Doc Farwell's, having my last solidify and go to waste.. Two days ago I dabbed the top cuts of 3 whip & tongue scions with an interior semi-gloss latex paint. The only difference I could detect was drying time; the paint took longer than the latex grafting sealer.
Perhaps if you mixed in some liquid latex, which isn't too expensive, it would dry faster.