As someone has pointed out in the post's comments, there's the Wombat ADB-USB converter as an alternative. Doesn't look as good, but requires no battery or other power supply. IIRC, it does distinguish between left and right Shift/Command/Option keys. Quickly looking at the product page I realize that it even converts both ways, so you can also use it to attach your USB keyboard to your ADB Mac or NeXT.
As someone has pointed out in the post's comments, there's the Wombat ADB-USB converter as an alternative. Doesn't look as good, but requires no battery or other power supply. IIRC, it does distinguish between left and right Shift/Command/Option keys. Quickly looking at the product page I realize that it even converts both ways, so you can also use it to attach your USB keyboard to your ADB Mac or NeXT.