I can't find the Carja war bow in Horizon Zero Dawn. Where and when in the game can you buy one?
This is the Blue variant of the weapon and can be obtained after reaching Daytower for the price of 300 Metal Shards, 5 Desert Glass and 2 Slagshine Glass. It has 50 handling and 2 mod slots.
I can't tell you for sure which exact merchants will have it available, but the Meridian merchant sells all weapons available, so if you can't find it elsewhere, go there. Being the Carja War Bow, however, (and based on the guide), I believe you can find it at any merchant in Carja, as the Daytower is the gate into Carja territory.