I had a pocket J-pole I built back in 1980, out of home grade twin-lead. That antenna worked great, had about 10dB of gain over an IC-2AT rubber duck antenna. Worked well for years. I built a J-pole variant about 10 years ago, and it worked well, too. It consisted of a QW coaxial stub instead of the usual open wire stub. The stub was around 12" long for 2M, shorted at the bottom, and fed about 1.25" up from the bottom with coax. The antenna was around 39" of wire attached to the top center of the stub. I hung the antenna from the inside 9' ceiling for testing, and it worked very well, at least as good as any other HW antenna. That antenna would be easy to build and mount inside a 3/4" PVC pipe, with a ferrite placed at the feed point.