Have you considered a “generic” pre heater?
If you are satisfied with having an autonomous system to keep your heat exchanger free from ice (by keeping the air intake temperature above freezing temperatures), it should be possible to install another brand of preheater.
This would naturally make any intake temperature measurements invalid, when the preheater activates, but I find this an acceptable trade off…
I have been looking at an “alnor” unit, which cost around 1/5th of a Danfoss.
But with the current state of winters here in Denmark, I will wait and see if it becomes necessary…