You can make your own.....I used this mix.

https://www.youtube.com/watch?v=kbe5L9UyyVQ

I do 60 percent boiled linseed oil, 30 percent oil based polyurethane, 10 percent turps. I made 200 mil....120 ml linseed....60 ml poly....20 ml turps....shake. Was very thin...leave top off container for 3 hours and thickened up nicely.