I made my own, pretty cheap with parts from Amazon:
One plug in the oil filler, one in the breather. You have to plug the "intake" in the aquarium pump to make it a closed circuit. I put a filter on the end of the tube in the desiccant bottle to keep any silica out of the engine.
I've had it in use for 2 years, just now regenerated the silica beads for the first time.
There is a fair amount of moisture in the tubing when it is first connected after shut down.