Not related directly to the ASIAIR Pro since I don't source my 12V from the ASIAIR itself (I use a combination of PowerPoles and the deepskydad DC power hub which uses a 2.5mm center pin to handle the 12V input instead of a 2.1mm center pin connector), but I have been using the anti-dew strips that Amazon sells for camera lenses, made for USB power.
I found a camera lens anti-dew strip at Amazon that easily fits a 115mm diameter dew shield for my larger refractor; and smaller ones for my WhiteCat51 and Borg 55FL guide scope were even easier to source at Amazon. It may be difficult to find a camera lens anti-dew heater if you use something larger than a 100mm refractor.
I then used this to adapt 12V to 5V:
https://www.amazon.com/gp/product/B0758ZTS61
A word of warning that configuring that board for 5V operation is challenging for old eyes (you need to cut a really tiny shorting bar on the PCB to remove the potentiometer and then apply a dab of solder to bridge the fixed 5V selection -- you may be able to put the potentiometer to good use though, if you don't need full heating from the dew strip, if you trust the potentiometer to hold its value in the damp and cold).
WARNING: do NOT apply 12V directly to the USB powered anti-dew strips. The heating elements (resistors) are not usually rated to handle the higher power, and when one resistor fails, it could cause a thermal runaway. At least use a 7.2V Zener diode or something in series (if you are running off of house current and don't mind wasting power).
If you don't mind a little bulk, this next converter should also work, and it is pretty much turn key since its 12V input uses a 5.5x2.1mm connector. I have one, but have only used it inside large waterproof NEMA box together with ASIAIR, a mesh router and USB and power hubs, which keeps the inside of the box warm through the night; I have no experience with it in the cold:
https://www.amazon.com/gp/product/B07SS6XTZY
I did find that one of the Amazon camera lens heater controller timing itself out after a little while (I don't remember which brand now; I think it is one of the smaller straps that I used for my guide scope), but since I had lopped the controller off and applied 5V directly to the strap now, it works for me. If you are using an Amazon one without modifications, test to make sure it remains on through the night.
All that being said, Hutech (the USA Borg distributor, if you are not familiar with Ishikawa-san's work) now sources an anti-dew heater with a very interesting controller (with settings for absolute T and delta T; most anti-dew strips just applies constant power to the heating elements without reading back the actual temperature):
https://digiborg.wordpress.com/2020/09/23/more-blue-smart-lens-heater/
https://astrohutech.store/product-category/telescopes/8-more-blue/more-blue-smart-lens-heater/
I probably would have gone this route if they were available when I bought my anti-dew strips. I still might pull the trigger, ha ha.
Good luck with your hunt.
Chen