It's probably easier to just try a few of the most likely cheap substitutes than try to understand all the chemistry.
The cheap Krylon Clear Acrylic spray might be worth trying again, but I found some of those I once tried to have such bad nozzles that even if the chemical was equivalent, the final product was not. Blick and others seem to have house brands.
Lascaux is B-72 (the real thing). I have no idea if there are newer formulations that have been able to exceed its performance.
Paul