Thanks for the info. Definitely not worth the price! I'd rather splice together something in parallel with the current battery and charge them manually.
Now in Jan 2022 all of the web sites in the replies to this request are gone, as are those of three other sellers found by Google. Like many (?) other people, I would like to buy a new OP-MP9-EXTBATT (or even the standard battery) at literally any price. Sigh ....
There is a standard battery for sale on eBay fron UHH...or you can just go to the source...
Usedhandhelds.com and buy direct, both standard and extended batteries...
Clevo, by the way, is a 3rd party manufacturer who has made generic copied hardware components for portable computers for years. They produce lots of laptop batteries.