The thickness of them are all the same. The thing you want to look for is how many mm wide it is, and how long it needs to be.
Our local supplier sells it by the ft - I think all graphtec models are the same width/thickness, it's just summas and Roland's that differ.
But if you want to be sure... Measure how thick it is, the width and then the length. Send them the measurements and they should be able to cut you a strip to size.
Keep in mind if you have a 54 inch cutter, odds are you'll need a 65"+ strip, so actually measure instead of going by the length your cutter is rated for.
You can even buy strips on eBay, or sites like uscutter - I have a strip I ordered from China for like $5... I haven't used it yet, but it feels the same firmness / quality as the official ones. That being said, I'd go for the official brand, it's not.much more expensive if you can get it in the length you need.
I believe grapghtec even sells them directly... Fire off an email to them and ask what size / part you need, and they will know for sure.
