Hi,
apologies for the delay. For Ar/CO2 (85:15) you can use the mobility file for Ar+ ions in Ar. In reality things are quite complicated, see for instance this presentation
but the Ar+ in Ar mobility values happen to be quite close to measurements. For Ar/N2 I don’t know, but I would perhaps also use the Ar+ in Ar mobility file as a starting point.