I just went through this myself. I ended up going full redneck, chucked up the factory 2-groove pulley in my drill press, and cut the outer groove off with a cutoff wheel on an angle grinder (I have no access to a lathe). It worked out perfectly, but shortly after, I found out Powermaster sells single groove pulley's for the Denso 17 mm shaft - #181, #182, and #183, depending on what OD you're looking for.

Keep in mind that a Bosch 17mm ID pulley may not work because the Denso alternators are 'domed' in the front, so the pulley needs to be dished on the back side for clearance.