FYI, you don't need it to circulate. Any heat source, whether applied to your radiator fluid, engine block, oil, etc. will propagate throughout the engine and coolant via conduction. I apply heat, via an electric heater, to one part of the block and in short order, my temp gauge will show temps rising and that probe is on the opposite side of the engine up in the thermostat.
Heat moves to cold. Apply heat to any portion of the engine and the entire engine, oil, coolant warms. Plus you don't have to carry around your heat source (circulating antifreeze heater and plug) 100% of the time you ride. Plus you don't have yet another cut hose and hose clamps which is one more point of failure. Plus you said room is tight so an on-board solution could be finicky. Plus since you would have to run an extension cord to your trailer anyway for your solution, also carrying a little cheap fan-driven electric heater and setting it beneath your bike isn't really any extra work.
If you still decide that an on-board plug in heater is what you want, a non-circulating heater or a block heater (they have magnetic ones) will do the same job. No need to circulate.
For anyone that the electric heater solution sounds good, just set a heater pointed either under your bike or on a crate next to it pointed right at the engine. Even if you have an engine blanket, there is a gap by the exhaust pipe. Set it on the pipe side and point it in the gap in your engine blanket plus some of the heat will be hitting your radiators. Plug it in when you first get up and by the time you are ready to go in 30 to 60 minutes, it will start up just fine.
If you are trailering a long ways to a place without electricity and in an enclosed trailer, when do the heater at home before you leave, start the bike and let it warm up to operating temp. Since you are in an enclosed trailer away from wind, the engine will start way easier at trailhead even if an hour or two away.
