check the ingredients, and post them. otherwise, windshield wiper fluid is mostly methanol; you'll likely find a source of usable methanol at an auto parts store. for the psilocin extraction, glacial acetic acid and methanol are the two reagents necessary for a pure, stable psilocin salt; that's a good project.
What do ya figure it would be in? Do you think the thread starter could just ask for methenol? Is it used as a gas additive or something?
yes. methanol is one of the best octane boosters; if you know anyone who's into racing, they may know where to get pure methanol; otherwise, ebay is the best place (cheaper than chemical supply houses, that's for sure) methanol is used for so many different things, so it's not exactly watched closely.
As mentioned earlier, it is sold as "Dry Gas" at auto parts stores, for removing water from your fuel tank in cold weather. Check the label to be sure you get MeOH, not IPrOH. Methanol is also an ingredient in biodiesel manufacture, so hippie-looking folks buying large amounts of the stuff no longer raises the eyebrows it once might have...