Sears, Western Auto, and Northern Hydraulics all offered (2) PTO Generators. I believe a 20KW, and a 50KW. They work well, except that frequency regulation was dependent on how well the tractors govenor worked, or if it had one. If the load changed, so did the frequency(Hz). They show up on E-bay fairly regularly, and there may still be New Units available from W.W.Graingers.