It is finally out after 8 years.

Extra 10% off on Steam if you own any previous Mount and Blade title. (Targeted)

Greenmangaming also has the game, 17% off / $57.92 : https://www.greenmangaming.com/games/mount-blade-ii-bannerlo...

If you have an account on Greenmangaming, click VIP for extra discount, down to about $51 AUD.

Please be aware this is Early Access version and the game is still in development.