[Willow is very much not a fan of guns based on personal experience with them, so this makes her go quiet for a moment, but she keeps her thoughts to herself and just answers his question.]

They don't really use them, but if you want bullets you might be able to convince a blacksmith to make some for you? [she suggests, swallowing her dislike of guns.] It might be a little pricey, and I'm not sure how well they'd work... but check the crafter's district. I'm sure someone would give it a try if you gave them enough money.