You are going to have a difficult time finding a polycarbonate tube for this tank. First of all, it's a relatively uncommon tank size. The 3.5ml and 6ml Smoktech DCT's are much more common. Most manufacters and vendors selling cartomizer
tanks have been switching over to the polypropylene plastic, pyrex glass, or stainless steel tubes that are immune to the cinnamon and citric flavors that attack the clear polycarbonate material. I took a quick look at some vendors that used to sell polycarbonate replacement tubes, but they seem to be discontinued.
I don't know how many
tanks that you need to replace the tubes. If you have several and are really attached to them, it might be worth replacing them with pyrex glass. Otherwise, either put up with the frosted appearance or go with brand new
tanks of either stainless steel or pyrex.
Your only recourse might be to contact OCD, the glass expert at IBTanked.com. He has been collecting glass tube stock to help owners of the older and newer tanks that had/have the polycarbonate tubes and RBA tanks. His glass products have proven to be inexpensive, but you may likely pay $7 - $13 for each tube that you need.
You can find him on the E-Cig Suppliers sub-forum here:
http://www.e-cigarette-forum.com/forum/e-cigarette-suppliers-forum/339809-do-you-fiddle-your-thingy.html or go to the website
IBTanked - Get Tanked With Us! and find the section on custom cut tubes under the store menu