I noticed today that Outdoor Shooter Supply’s house brand - Red Stag, now comes with the potential of custom headstamps. From the “Gunbook MSR” website, they show a custom Red Stag headstamp on 6.5 Creedmoor, which is new, but also they mention that they can do custom headstamps of any sort of 6.5 Creedmoor in small lots of 100, for around $75.00 Their info seems to indicate that they receive blank brass from one of the major case makers, and that Red Stag then adds their own headstamp somehow. You can order your own name, or put dates on the headstamp, whatever you want. They mention that 6mm Creedmoor and others will come soon with this option.
I also see they are custom headstamping wildcats like .358 Yeti and .375 Raptor.