By now you may have found a source for the ammo. However, if
you have not the following should be a help.
The 7.65 x 21 is a 9mm, but with a bullet diameter of .312.
It is a bottleneck case just as is the 8mm x 22 for Nambu
pistols. The 8mm Nambu round is a .311 bullet diameter.
In reality, all of the metric ammo has a problem that
from one manufacturer, or one caliber to the next the
actual size of the bullet diameter can vary widely. Unlike
the U. S. caliber designations where the actual bullet
diameter may not be exactly as it is called, the actual
dimensions are always within the same specs as every
other manufacturer of that ammo. Such has never been
the case for any of the metric ammo manufactured.
The 7.65 and the 7.62 21 or 22 lengths are both within
the same caliber tolerences with either varying from
.309 to .315 inches. The fact that the 7.65 x 21 and the
8mm Nambu are both the same bullet diameter for use,
and both are bottleneck cases, to use the 7.65 x 21
brass and full length resize it to a straight case will
make it into the diameter you need with a case length
of the 22 you desire for your pistol. Just be sure to
check the length and trim if it is needed, and double
check the head for size. The rim should be the same
as your 7.62 x 22 brass.
Always use good dies and always use good guages to
insure sizes.
Good luck.