Bartley Paste Wood Filler Replacement?

I just ran out of Bartley's, have two Les Paul's to refinish, and Bartley's seem to be out of business.

Both owners want me, as much as possible, to use the original 50s materials and methods. This means, among other things, mixing a non-colorfast aniline dye into an alkyd pore filler.

Bartley's ingredients include alkyd resin, calcium carbonate, kerosene, mineral spirits and polyurethane.

Cardinal Pore Filler (LMII) looks interesting, is alkyd based and thinned with mineral spirits but that's all I can find about it. LMII suggests coloring it with their Universal Tints which only comes in white, black, umber, brown, and sienna.

I've looked at many other fillers but none offered much info. Recommendations much appreciated!