American Fabric Filter Co. offers heavy-duty bottom collection bags for dust collectors in either plastic or canvas. The 6 mil thick polybags, available in rolls of 50, are stocked in 2 standard sizes (21" D x 50" L; 24.5" D x 72" L) to fit most units. These disposable bags are strong enough to stand up under constant use and contain wood waste from chips to fine wood dust. The clear bag allows you to see when it needs to be emptied or replaced. AFF also offers collector bags sewn of rugged cotton duck. The canvas bags are reusable, making them more economical, and custom sizing guarantees a perfect fit.
More information is available here.