Randuf,
From the photos I can see on the internet of a Markill Devil, it's just a standard canister gas stove -- a very popular type of stove.
A lot of the brands say "only use our gas," but that's more legal CYA and marketing than anything else. The fact of the matter is that you can use any gas canister with a standard 7/16ths threaded connector. The following brands should work with your stove:
Jetboil
MSR
Coleman
Primus
Snow Peak
Optimus
Glowmaster
Brunton
All of the brands are essentially interchangeable, and it doesn't matter which one you choose except in colder weather (50F and below) when you want to avoid regular butane and only get isobutane.
Hope that helps,
HJ