This comes to mind.....Get yourself a small carbonator motor, a procon pump (1 gpm would be more than enough), A bypassing regulator to control pressure/flow, a motor contactor, and some 1/4" poly tubing to go out to the bays...You might also consider a prefilter to filter out any crud that would plug a tip, it would go between the pump and poly tubing...Do you have a weepmiser? If you did, you could control the motor contactor from output 2 set at whatever temp you want it to come on...Of course you would also need a check valve on each poly tube connected to the HP hose above each bay. I guess it wouldn't matter if it ran continuous below set point. Even those little 1/3 hp carbonator pumps run 5.6a....Something to consider when running continuously.
Given that, you might also look into the small Taco pumps. Since you don't need much pressure, they use a lot less current and are rated for continuous use. There are many to choose from. I get mine from Supplyhouse.com or Pexuniverse.com for my floor heat. You'll have to look at the output pressure and amount of water needed taking into consideration any "Head" restrictions you have. (elbows, fittings, elevation, etc...) FWIW....I weep 20oz per minute out of each wand...