I just was just trying to find replacement batteries for my HTC Vive controllers. Having them now for over two years I noticed they do not stay charged for as long as they did earlier and eventually I would expect them to not work any longer. So out of curiosity I began to search and found that I could find replacements now from germany ebay for 9.95 euro and 20 euro shipping thats over 30 us dollars, and they simply are not available in the U.S at all at this time. I write this in the hope that when Pimax finally releases there own knuckles style controller or whatever, that they at least consider making replacement batteries available for their customers. I am confident I could replace the vive controller batteries but their cost is to high for now, so I will wait probably until they fail completely.
Edit just bought two from UK ebay came to 50 US dollars (including shipping).
I would also like to add that the state I live also has write to repair legislation that requires manufacturers to provide the components and accessories available to consumers allowing them to repair for example tractors and electronic equipment. Many companies simply do not want their customers to be able to repair their own purchased items themselves this legislation guards and protects the consumer.