Bonus: they sell cabinet tip screwdrivers in the common slotted and Philips sizes.

Edited to add: Snap-On also makes good screwdrivers, and your friendly local garage can probably tell you when the Snap-On truck comes by </edit>

If you need quality slotted screwdrivers for slotted screws with both the width and thickness of the blade specified, you'll likely need to find your local gun and ammunition store (and they'll likely be a special order even there).

Gunsmiths and sewing machine repair people are just about the last people on the planet who care about the blade fitting the slot well in both directions for a wide variety of screw head sizes.

edit: looks like Wera tools specifically are sold by a bunch of different people on Amazon, NEMobile, and BCFasteners are a couple that I've seen, so really no idea what you're getting.