Not sure if this is the right area.... but is it possible to buy "security chain"? Something like on these: https://www.kryptonitelock.com/Outlet...=1002&pid=1168

I'm not sure I understand the question? You can buy that chain right there on the website you linked.

If you're asking about buying raw chain by the foot, you can do that here (cheap!): https://www.bikeregistry.com/estore/p...31fc26a7d309c2

Or here, with cordura cover included: https://www.bikeregistry.com/estore/p...31fc26a7d309c2

Thanks! That's exactly what I was looking for.

There's also the Planet Bike Transport/Storage Chain. The $59.99 MSRP is pretty steep, but I was able to score one for 31 bucks from MEC.

For a larger selection and bigger chains (and ground anchors) can be bought below:
https://www.elitesecuritysupplies.com
https://security-chains.com

+1 bikeregistry - highly recommended.

also, you might want to check out https://www.mcmaster.com/ - look up "security chain". they've got 7mm & 10mm square link "Cut-Resistant Security Straight Link Chain" by the foot.