On March 9, 2018 at 09:38, Short Stop said...
You can get any length and diameter you need from a pipe shop
Or, for one or two pieces, often even Home Depot!
and they'll thread it for you on the spot. Pair it up with a floor flange so you can bolt it onto any surface and your good to go. Make sure to cap the end (bottom) with a threaded cap for safety.
Where does the cap at the bottom end go in relation to the floor flange?