I notice that BestBuy no longer carries the replacement battery for the Pilot. I suppose buying an old unit on ebay would suffice for awhile, but it's not as good a solution as a new battery, and as a source the batteries in those units will become a worse solution over time.
It's inconceivable to me that the same battery isn't used in other devices. I tried to track down a source through a web search but had no luck. Maybe someone will be more successful and post the results here.