I too am interested if there is anything online, all I can find locally are 9/16 -18 NF which is great for the larger 9/16 barbs, but for G1/4, closest thing I can find is 1/4"-18 NPT which sort of works because most barbs are so short, but it's not perfect and I want and BSPP 1/4-18.

McMasterCarr has them for $17 plus shipping, but man that seems a bit steep. Looks like I'll have to special order it, I'll see if I can do that with one of the local stores..