Not owning a Polarion light, I can't say what battery was used, whether it was a NiCad, NiMH, or lithium ion.
I have a few older lights that haven't been used in years that were NiCad powered. All of the batteries are dead and won't take a charge. My Nighthunter One used a 20 volt lead acid battery that died. Xenonics doesn't like to sell to civilians, don't have any betteries in stock and when they become available next year will be $550 each. I built one from new lap top batteries and a PCB and found a lithium polymer battery that fit inside my light.
All of the short arc lights being sold use a proprietary battery. They are proprietary, because when they were designed no commercial battery had the amps or voltage required to run the light.
Your choice, purchase the battery from Sparetech, or find someone that can rebuild yours. Otherwise, sell the light and purchase a light that uses 18650 batteries.