Ah ha! I had emailed them about that very topic.

You can get septas fairly cheap if you watch eBay. 13mm should work for these, if they are standard sized. Luckily, I happen to have some left around from when I was talking about vials a few months ago. Barring that, 0.05" teflon sheeting and a 14mm punch, and cut yuor own.

Still, not much of an advantage compaired to buying through someone that gaurentees teflon.