I've got this tank, and it's a bayonet-styled twist top, if I remember correctly. I haven't heard of any new caps, but considering SXK and WeJoytech made these clones over 6 months ago, I wouldn't expect anything to be included that wasn't available at release.

I like the bayonet design, once you have it in your hand, you just turn the cap, while slightly lifting - it's a piece of cake.