well, I found this one for only $3.84 from health cabin (yes, I know they take forever to ship)
how does it look?
3.5ML 510 DCT (Dual Coil Tank) Cartomizer MOD(1.5/2.0ohm)
From the image and the description, that tank is the first version of the Smoktech DCT tanks. Black delrin endcaps and a clear polycarbonate tube. I had one like it as my very first tank. It lasted about a week before the polycarbonate tube warped and leaked
juice, necessitating throwing it away. Your luck may be better.
I'd recommend the polypropylene version 2 sold by My Vapor Store. The tube is frosted and not clear, but the plastic is stronger than the original version and is immune to the effects of certain flavors that can melt/crack polycarbonate. If you already have XL length cartos on hand, they do offer just the tube and end caps without a carto for a cheaper purchase ($8.55).
Pro DCTank Tube