What is the Solubility of Common Noble Gases in Concentrated Phosphoric Acid, 85% w/v?
Value seems to be $k_H^{\ominus}=4.3\times10^{-3}\;M/atm$ for Xenon in water.For it in conc. phosporic acid seems not to be available as probably no one has carried the experiment in this solvent since water is most common and used commonly.Maybe you would?

Also, A simple way to describe Henry’s law as a function of temperature is:
$$\LARGE k_H=k_H^{\ominus}\times e^{\left(\frac{-\Delta_{soln}H}R\left(\frac1T-\frac1{T^{\ominus}}\right)\right)}$$
where $\Delta_{soln}H=$enthalpy of solution. Here, the temperature dependence is:
$$\frac{-d\ln k_H}{d(1/T)}=\frac{\Delta_{soln}H}R$$



Useful Links:
Table of constants, The NIST Chemistry WebBook, The Pesticide Properties Database (PPD)