I’m also partial to Sutherland Welles products and have been a long time acquaintance/friend of company founder Frank Welles, plus have worked together on a couple of wood finishing projects.Watco makes a Tung Oil Finish as does Minwax.
You’re right that Waterlox is dark and I sometimes wonder why since it likely contains more Tung Oil than the others. I still like it best though.
I really like Sutherland Welles Polymerized Tung Oil. It’s tung oil that’s treated so it dries in a short period of time unlike pure tung oil. It’s light in color, pops the grain and makes nice gloss.
Test whatever you use on a scrap piece or inconspicuous spot. Teak and other oily woods Have a way of causing finishes not to dry properly.
The closest equivalent products to Formby’s in the Sutherland Welles line are Murdoch’s Hard Sealer, Hard Oil, and Wiping Varnish all of which are a polymerized tung oil/urethane alkyd blend. Murdoch was Frank’s uncle. I’ve used several of their non-film forming finishes on teak and other exotics with great results.
Formby’s is essentially mostly solvent with a splash of tung oil and alkyd resin, and not a tung oil per say, but more of a wiping varnish.