I just sent off a Sig 320 carry slide to jagerwerks to have it milled for a Trijicon SRO sight. Anyone have any recommendations as to a holster for the combo?

Not specific to your query. But I have found having an optic mounted is not a problem for holsters in general. My bladetech inventory didn't have issues when I added an RMR to a G19 or a G17 or an HK or a full size 320 etc. etc. But almost all of the holsters I own struggle with the increased height of adding suppressor height sights to the gun as the channel is normally not large enough for that.
I've been lucky with a few, but its hit or miss.
red hill tactical has built me a few recently and they have the option to specify suppressor height sights and the optic so its pretty likely that will work. I didn't check if the compact 320 is in their options so you should confirm that. The classic bladetech OWB for the full size 320 has no problems with either a mounted optic or suppressor sights(also available for the compact, but I have not tested it, only the full size). FWIW

What he said. Bladetech is fine. None of the ALS Safariland stuff will work, which sucks. I looked at modding one but I don’t think that is feasible. Any lower, or race cut kydex should work.

Bladetech is probably the easiest for sure version that works.

DeSantis has a belt slide for optic guns. I have one and its pretty good.