I don't think that one exists for any Volvo nor do I believe that one's made for other cars either for that matter.
Volvo DOES make a new "kit" for your car which includes a new accumulator BUT not only does that part become saturated if opened for about 20 minutes, so it must be the last part to be installed, the system MUST be evactuated with an AC vacuum pump for at least 20 minutes or moisture will be trapped inside the system AND moisture with 134a PAG oil becomes acidic (known fact). That acidic mixture will eventually disolve solder joints again from the inside out and within 2-4 years you'll be needing yet another evap.
That kit also incudes a pollen air filter kit and blower motor brush air restrictor (plastic tape).
The kit adds more $$ to the project but is Volvos latest and greatest "cure" for the problem.
If you or anyone find a copper evap for an 850, do post it here but I highly doubt that anyone makes it for two reasons; poor demand for a limited production part (only Volvo 850s/X70s would use it) and it might not absorb heat as well as the aluminum evaps do thus not work well.