Hey, Anthony,
Dynamat is a great product and still available, as are several alternatives with lesser known names and much lower price tags.
Since it's going under the carpet anyway (and if budget is any concern), you might want to look at an unlikely alternative that I have used successfully. Frost King FV516 Duct Insulation Self Adhesive Foil & Foam comes in 12" wide, 15' long rolls and costs less than a fourth of typical Dynamat prices per square foot.
I picked mine up at Home Depot but you can also order it on eBay if you don't mind paying shipping. Here's a couple of links:
https://www.ebay.com/itm/143861344477?chn=ps&norover=1&mkevt=1&mkrid=711-213727-13078-0&mkcid=2&itemid=143861344477&targetid=4581115207302808&device=c&mktype=&googleloc=&poi=&campaignid=410490119&mkgroupid=1240249342282558&rlsatarget=pla-4581115207302808&abcId=9300491&merchantid=51291&msclkid=c3d71355df241c9c5dbc73df43ae62c8
https://www.ebay.com/itm/393194074439?chn=ps&norover=1&mkevt=1&mkrid=711-213727-13078-0&mkcid=2&itemid=393194074439&targetid=4580771609030758&device=c&mktype=&googleloc=&poi=&campaignid=410490118&mkgroupid=1234751784804585&rlsatarget=pla-4580771609030758&abcId=9300491&merchantid=51291&msclkid=3fb635efefb51111aee05565742517f0
Good luck with your project.