From my previous Internet fu research, NU22B is a good replacement for R22, and claims it is compatible with any oil in compressor (mineral or Polyolester (POE)), where using R407C recommends adding POE on swaps. The old oils and R407C aren't really that compatible, hence the need for the POE with some of the new refrigerants. Newer or drop in compressors are generally manufacturered with POE. Some of the ECU's came with R407C (newish) and some have older R22. Check the plate and refill. There is still stuff around for pretty much any refrigerant, some require a HVAC license, the newer stuff is generally more accepted to be sold over Internet because it's way better than R22 (phased out in 2020) for the environment. I still see a lot of hesitation from HVAC people to switch gases regardless. I was lucky as mine was R407C, so no decisions for me.
rsms - me either, not a HVAC expert, just got really Internet smart on it lately. HVAC / refrigeration is a pretty in depth field.
What was the prognosis Shawn? Any luck with an HVAC guy? I am curious to see how my DIY stacks up to their prices.