The trick is not to talk to them, alot of the people you deal with at Home Depot and the like are pretty much totally mentally taxed taking care of duties like "breathe in, breathe out" and avoiding walking into shelves, walls and mechandise displays. Show them the key and say I need one of these made, telling them what kind of car adds a whole other world of intelectual complexity they just can't handle.
Look for the older guys, they usually actually know something, that and the aprons they wear are there to keep the work off of them, try and find someone without an apron
And if you live in Squamish and have to deal with the mountain building center there do yourself a favour and drive into Vancouver...