I'm guessing you're not in the US, since batteries here are still avalable.
Doing an internet search on the actual battery model number (EVE188595QH) that can be seen on the iFixit battery page, there are many sites that sell it. Most of the ones I saw were on eBay, but there was a listing for what looks like the identical battery being sold on AliExpress.
Newest EVE188595QH Battery 3.87V 2050mAh for Zhenyao E-reader Kobo Libra Colour - AliExpress 509
A search using the phrase "kobo EVE188595QH battery" turned up a wide variety of sites selling it, so pick one that suits you.
crwdns2934105:0crwdne2934105:0
crwdns2934113:0crwdne2934113:0
crwdns2915270:0crwdne2915270:0
crwdns2889612:0crwdne2889612:0
0
crwdns2947414:01crwdne2947414:0
Thanks so much for your advice, and yes, you're right, Jerry. I'm in Australia - and on the ifixit Australia page, they're out of batteries. I have bought a battery already - did lots of research and bought one - waited months, only be to delivered the wrong one. :( I think that was through Fruugo. Maybe it's worth one more shot through a different supplier! Are you sure those numbers are right???
crwdns2934271:0crwdnd2934271:0 Liezl Shnookal crwdne2934271:0