I've made 'em from scratch from C-360 brass. Making metric threads on a Atlas-Clausing lathe is fun!When I swapped my half-bridgeported rotary engine into my RX-7, I had the pressed-in factory jets in my Nikki carb yanked and the hole tapped for metric bolts. Then I bought a set of numbered drill bits and a bag of phillips-head machine screws and drilled my own jets.