You can find the shop at Horseshoe Perch, on Horseshoe Lake east of the city of Demeniss. The shop is on the stone perch protruding into the lake.
Requirements to Access
The entire Demeniss region is hostile and enemy soldiers will attack you on sight everywhere you go. But you will be able to interact with this vendor (and all other regular ones in the region) from the start of the game, it will just be more difficult to escape combat with all those patrols everywhere.
This ends when you complete Chapter VIII from the main story. After that, you will be able to freely explore the region and visit all shops.
