You can locate a replacement for the external filter from all kinds of sources. Here's one example.
http://www.rickscamaros.com/camaro-c...1970-1981.html
Is the L[]C version white? One of the filters I got is. It's more rigid than the fiberglass version.
I got one with the filter built into the part that pops onto the bottom of the canister. These have a drain (or breather tube). Basically like the one in this link but half the price. Mine is a replacement, NOS Standard.
http://www.ebay.com/itm/NOS-Vintage-...2NrZKQ&vxp=mtr
I've got one canister that has what I believe to be the original bottom. This doesn't contain the filter. Again, it just pops onto the bottom of the canister.
My original canister didn't have the bottom. Held up real well regardless. In fact, of the three it was the only one w/o a tear in the inner bottom filter element.