well basicly dynamat is preglued rubber sheets that u just stick on your car right? so if i went down and picked up some rolls of rubber (i dont know what yet i havent looked around) and used spray adhesive to glue it down to the car it should work the same shouldnt it..
there is an alternative called "Semar's Secrete." it's at home depot in the roofing materials section (behind the lumber section). look for "press and seal." it's tar paper w/adhesive like dynamat. 6"x11'
dynamat takes the sound wave and converts it into heat...it is a tar, not rubber, try what mikechec9 suggested. the metal definately helps it from being extremely messy...especially when its hot...like in NY right now, feels like 100 lol too hot...and sound dampener gets soft and messy.