When I was 16 and lived in Bragg Creek, I had saved up for 2 years to finally buy my own truck (with a little help from ma and pa

) With my $3,500 used 1989 Chevy Silverado 1500 in the drive, my dad recalled that he had seen a box liner in the woods near our house, collecting leaves.
So we trekked down the hill, retrieved the folded and demented truck liner to see if it'd fit. When we chucked it into the back, it sat there all bent and not fitting. I hopped in the back of the bed, put some pressure in the middle and that baby sucked right up to the sides, a perfect — and free — fit.
Little water to clean it out, looked great.
So my advice, check your local forest first.