IOC carries the Miller 252 and the Lincoln 256. https://www.weldingsuppliesfromioc.com/lincoln-power-mig-256-welder-package-k3068-1?utm_source=google&utm_medium=cpc&adpos=1o1&scid=scplpILIN20140012&sc_intid=ILIN20140012&gclid=EAIaIQobChMI7dnkxbGH4gIVRbbACh2Y4wRPEAQYASABEgLBn_D_Bw...

To find orifice diameters you can also use a set of number drills. No need for a micrometer then.