cargo covers are a beast to ship... so big and flat. Best thing to do is either wait and see if someone on here has one for sale, or try your local auto junk yard.
after doing a quick google search, i saw a few on automotix, but wasnt able to find any on mazdastuff or onlinemazdaparts, unless I wasnt looking hard enough.
If you really want it now and you dont mind paying more, Im sure your local dealership could order you one.