Nowhere... just ordered mine after looking in Canada from ZRP in the States. Just received them and they look good, but not cheap after exchange, customs and duties...
There isn't a lot out there to pick from. I cut my own set last year out of aluminum and then powdercoated. Finished a few vents a couple of nights ago and hope to print them tonight if I get a chance. Curious to see how this works, I have printed other parts in the past, but haven't done a set of vents yet. Found some yellow that is pretty close to the yellow on my 17/18 X