Kevin,
If you got a Wall-Mart or a Target store you will find them there and You will never need to buy quiver replacement foam again...I did another search lastnight and found those yoga blocks for around $3.95 each but cann't remember the site...I'm thinking if you buy 10 or 20 you can make a very nice backstop target also...Just search the Yoga block and prepare to make new quiver hoods and replacement vitals for your 3d targets and it's cheap and feels just like the rinehart material...  

Hey Frank, will recycling centers just give you stuff like that? Might be worth looking at.

Thanks for the tip...

Keefer, thanks for the yoga block tip!!!  Good stuff.

Dow chemical makes an insulation product called Sill Seal. You can get it at any lowes store. It works good but is only 1/4" thick so you have to layer it. It comes in rolls, 3.5,5.5 or 7.5 wide. You can use the leftover for stuffing in a bag target.

Also excellent foam for long skinny quivers is the seal strips used to close off metal roofing panels like "U" panel.Comes in 39" length.Can get enough segments to make three replacements for around 3$.
Mike the roofer

The phrase, "a wealth of information" definitely applies to what has been shared in this thread!