You might try well drilling companies. Well Casing pipe has a higher steel content. I bought a 4" well casing pipe ( sch 40) full length (21') FOR $60 at a place that sells used construction material to mount one of my dishes.
The WISP may be a problem if it uses the 3.65GHz channel.
WISP antenna is 920 MHz dual polarity... likely 900-930 MHz range. Radio us a Ubiquiti Rocket M900. They are fairly clean in the 3.7-4.2GHz range as far as I can remember. Think the model for the antenna is "intelletenna 900" or something like that. Fairly common WISP subscriber unit for rural areas where LOS is difficult due to obstructions or range.
Thanks Magic! I just submitted a quote on the metalsupermarkets website. Well see what these cats half to say tomorrow. They have a warehouse down in Richmond. I figure 10' x 3" id x 3 1/2" od. Hope i didn't confuse the guy. I have never bought metal before. Well except scrap cars that is...