There is no distribution by Surf-Pro for the 'Glue Buster" in the USA - its a Canada only product.
The MSDS (
http://www.surf-pro.ca/english/media/glue_buster.pdf) lists Methylene chloride (>60%) and Methanol (5-10%) as hazardous ingredients; the remaining components would be gel agents and skin forming compounds to reduce evaporation, etc.
Methylene chloride is hard to find in the States, usually it is a minor ingredient but there are a few exceptions, I've got it as sole active ingredient in an automotive gasket remover aerosol that I will try out.
There are also some of the paint strippers that still have it as the major solvent - read the labels & warnings, do some research to get the MSDS, read the labels, etc., and did I say read the labels?
And last, the new-to-me idea of covering the area with plastic sheeting is a great one, THANKS for passing that along!