John Verheul wrote:
I'm trying to fit a Reynolds Ouzo Pro integrated fork into a Specialized E5
frame, using a Ritchey Zero Pro integrated HS. The frame & headset are 44mm
bearing diameter, so that works...my problem is down at the crown race.
Ritchey uses a split ring as a crown race, which seems odd.

At least a few brands do this, I like it. It accommodates a wider range
of fork diameters, and reduces difficulty removing the race if the fit
is especially tight.

The fork has a
nice 30.0mm OD aluminum sleeve there,

That's to spec, IIRC.

which the bearing fits on perfectly.
When I put the crown race in there, there seems like there's too much space
between the edge of the head tube and the edge of the fork crown (1mm),

This varies, a little clearance is all that's needed but often the gap
is about 2 mm.

but
if I try it with no crown race the head tube rubs just a bit on the fork
crown,

Supposed to have the crown race in there to prevent that...

plus there's no 45' surface for the bearing to sit on.

The bearing works best with the 45 degree seat.

Do I have the wrong crown race?

No.

If so, where can I get a crown race that'll
work in this situation?

You have it.

To paraphrase Peter: Install crown race, assemble headset, go ride.