If not needed under 10 I'd make it manually like you say. For above 10 I'd make a jig to either cut and punch holes in 3mm plexiglass sheets, or a jig to quick

If not needed under 10 I'd make it manually like you say. For above 10 I'd make a jig to either cut and punch holes in 3mm plexiglass sheets, or a jig to quickly make cardboard moulds into which I'd place the pins and pour resin into. To me, either of the above is preferable to ordering 10k of them.