I am not aware of any place to get a sten tube, even the parts kits are hard to find and were mostly sourced in the 80's. Any tube that has the sten paper on it as an 80% is still controlled under the US atf laws for sale of machine guns. Harsh I have been looking for awhile, you can easily make your own with the right tube and overlay. If your not aware, once the tube and magwell are made these constitute a firearm and must be registered with the cfc, after this once your design is finished they may require you to send in the completed firearm for testing, if they can make it shoot fa or even slam fire it, they can determine it is a prohib and order it destroyed.
I am working on a hammer fired version that is semi auto, similar to the shotgun news one. If your good with machining you could make a SAS-3 OI style hammer bolt design. It is possible to get a sten with an open bolt passed the cfc for frt and registration but its complicated.
Hope this helps.
