Do any of my fedi friends (in Canada!!!) know a good place to shop for laptop batteries?

I inherited my Oma's Lenovo T420s and its battery is at 75% health and only lasts about 2 hours even in performance mode.

Edit:
So far my options are
1) eBay
2) Canada Computers
3) Newegg
4) laptopparts.ca
5) trying to find an original (through Lenovo's website?)

@dhampirdamsel I'm in the UK, so you may get different results, but there are several on Ebay for a decent price (about £15, so prob $20 or so). I haven't had much luck getting batteries from bricks-and-mortar shops, big or small, for quite a while here, but I HAVE bought a fair few batteries off ebay over the years with few problems. Canada may be different, of course.