I really like the recycled industrial cotton batts. They are slightly more effective than fiberglass for heat transfer, quite a bit more effective for blocking sound.
Easier to get than rockwool, which is also a good alternative.
Another bonus is that it's not all nasty and itchy.
This is what I used a package of:
Bonded Logic UltraTouch Recycled Cotton Insulation > Green Products, Green Building Materials | Green Depot
They have a warehouse in Portland where you could pick it up.
Green Building Materials in Portland, OR Green Depot
Will cost a touch more, but shouldn't be outlandish for the amount you're looking at.