Yours is an easy question *I* have a bit of a challenge in answering. At one of the clubs I belong to, old blue jeans' legs are sewn into "pillows" by shooters' significant others, and filled with masonry sand. The only affect on these is, on occasion, a too-hot barrel will scorch a bit -- but, other than that, they are exceptional -- and
the price is right! I have commercial bags made by Protektor which have worked awesomely -- save one, which a mouse (my guess?) chewed up a bit over one winter... I use TSC (Target Shooting Corp) rifle rest (
https://www.targetshooting.com ) which came with these, but I'd be surprised if any commercial ones wouldn't function quite nicely. Again, however, discarded blue jean legs, sewn, and filled with (from Home Depot) sand -- imho -- are hard to beat.
Just my experience, and suggestion...
geo