Did you check with all the PSI resellers who carried it to see if any of them have any left in stock?
If that fails, Rizheng makes a Polaris knockoff that's still available. Houtdraaiwerken Pen Kits carries it. Perhaps some other Rizheng resellers do also. You can probably buy it direct from them as well. I have no idea how it compares to the PSI kit in quality or appearance.