Sorry I can't find the video on youtube, but this is their product website, and it seems pretty feasible to make it yourself out of a block of wood and a razorblade.
Product video:
https://www.facebook.com/mobiletoone...3263979881831/
Kickstarter link with same video if you are allergic to Facebook:
https://www.kickstarter.com/projects...-bottle-cutter
If you can't watch the video for some reason, it demonstrates a simple device that turns a plastic bottle into a very long ribbon of plastic, which has considerable strength and many uses for bonding things together like rope.
Posting it here, because this seems like it would have endless applications for a SHTF or general emergency scenario.