Give the Midway one a look, it's on sale. I ordered one expecting something like a poly tarp but it was a lot better than that. It isn't quite as thick as the expensive one's but it is well worth the cost even not on sale. It also rolls up and is secured well and has a handle and shoulder strap, it's real convenient to take and use.
Been useing these old surplus paratroupers mats for years. They work great and are as tuff as they get! Did some checking and CTD and SG where sold out of these again. They are a little heavy but make great shooting mats as well as a fair backback.
The foam mats in this pic work ok the first time but tend to collect cactus thorns ;-(