"I think that you need to source one of the three kits using it from eBay or another rocketeer.
The three kits are:
a) Terrier Sandhawk (Estes 2083)
b) Python (Estes 2129)
c) Seahawk SM-3 (Estes 2149)
It appears that the last two kits were done for spare parts elimination, unfortunately. Semroc's ST-18 (O.D. 1.840", I.D. 1.800") is slightly larger in diameter than BT-1835 (O.D. 1.835", I.D. approx. 1.793" assuming 0.021" wall thickness). Unless you had someone checking with a micrometer, most people couldn't tell the difference. If you are trying to clone the Terrier Sandhawk, there are a lot of unique plastic parts in this kit. The Sandhawk section is a reproduction of the older (K-51) Sandhawk kit. The Terrier section has two-piece plastic fins and a plastic transition that was used in this kit and then SM-3 Seahawk. The fins were used on all three BT-1835 kits. Euclid could produce the tube, but their minimum order requirement is pretty steep (At least 1000 pieces, I think). Micromeister may know about that.
I actually compared the two tubes directly. The complete, but not installed motor mount on a Centurion F kit would not slide into the BT-1835, but it would fit with just a little sanding. As I said in my last post, the Estes is slightly smaller than the Semroc tube, but unless you are looking at both side-by-side, you would not be able to tell the difference. The outside diameter of the BT-1835 was obtained from the outer wrapper of the Terrier Sandhawk kit; the inside diameter was estimated by using the wall thickness that Estes normally uses (0.021") and doing the math.