Frank J Warner writes:

Best I've been able to find out, it's a mixture of naptha and acetone,
but in what proportions and with anything else?

Do those mix? Polar vs non-polar solvents?

Some MSDSs list n-heptane, so naphtha (note spelling) is a candidate.
Cleverly disguised as Coleman fuel at Wal-Mart.

Some MSDSs list ethyl acetate. Dunno of a convenient source for that.

Touching with a lip, eyelid, or other sensitive body part seems to reliably
kick off the polymerization.