I did the same thing Indy. Have a buddy that owns a Junk Yard. Went out there and pulled two bed liners off of trucks, grabbed the skill saw, and cut away. They work great. And best yet, they were FREE!
And, I'd actually say it's better, because you can customize the width for what you want, not feel bad about cutting them up, and you'll probably have extra for when they do get ripped up by someone's studs or for whatever reason.