Gases that are nearly transparent to solar AND thermal radiation?
Google Radiative (or radiation) absorbtion coefficients for gases (or enter specific gas of interest). Most of this data relates to applications in combustion and refrigeration so that is the area to look at. To avoid "contamination" from all the global warming stuff try looking at older things like papers from the 1950's. I have some detailed refrigeration books from the 50's which I think had this data but not to hand right now. Or see if you can get hold of some books like that from your library or a bookstore.

Many gases were studied in great detail with proper experimental measurements to verify well before global warming was a thing. You can find graphs of lots of useful things which can help you with an understanding of how the various gases might work in the atmosphere. For example using the emissivity of CO2 to calculate radiative heat transfer in the atmosphere with the standard Stefan-Boltzmann equation when you know the concentration of CO2 is, say, 400ppmV. Emissivity of CO2 can be surprisingly low at atmospheric concentrations, temperatures and pressures, less than 0.002 typically.