You can get any length and diameter you need from a pipe shop 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.

I just had a 10' pipe cut and threaded for a mount job last week. I used 2" pipe and that allowed me to use the same pipe as a raceway for power and signal. Ran BX for power through a drilled hole (large enough to contain a BX box connector) into a box mounted to the pipe behind the panel and drilled a separate 1" hole (with grommet) for the signal cable.