Many years ago, back when Edmund Scientific was still selling WWII surplus lenses, Cornelius aircraft compressors to make your own scuba tank compressor,and myriad other junk in the mid-60's, I purchased a smal surplus 2 pound gyroscope from them for $8, made a powersupply (if I recall it was 48v/400hz) and attached it to my camera+300mm lens. The spinning mass acted like 50 or so pounds of weight and the photos were rock solid even hand held. While it worked, the motorcycle battery I then used was a heavy beast to lug, so I eventually got rid of it somewhere along the line.
I decided to see if anyone makes such a stabilizer today ... indeed, Kenyon does and it looks remarkably like what I made exceptmy surplus gyrohad flat ends (not rounded) and was krinkle-black and somewhat smaller. See it here http://www.ken-lab.com/stabilizers.html