Actually, though Farmer's Reducer as packaged by Kodak isn't intended for proportional use, if you don't mix the solutions of the two packets it can be used that way -- as can homemade Farmer's Reducer. The difference seems to be in whether fixing of the silver converted by the ferricyanide takes place as it converts (cutting) or afterward (proportional).

Given the prices of ferricyanide and hypo crystals, I'm not sure why anyone would buy Farmer's Reducer (especially since the components are so useful separately), but if Kodak doesn't still sell it, you can certainly get it from Photographer's Formulary.