I would buy eDead. It is very cheap, and is almos the exact same thing as Dynomat. I have about half of my trunk done in eDead, and it worked really really good. My only tip would be is to buy a heat gun. The hotter you get the stuff, the less likely it is to come off after a long time.
there should be this stuff called Ice Guard at home depot and its weather dampening material (for roofs i believe) its peel and stick just like dynamat. the hotter you get it the better it stays on. some guy said he used 2 layers of it on his entire trunk for 50$ and had half the roll left. thats the road im thinking about taking