Jean is a peach and she has been very helpful when I’ve ordered with her. I bought my Pantone base colour set (as well as a few custom mixes) from Ernest Green & Son in Toronto.
With a local Kitchener office, Spicers is convenient, has my product ready for pickup within 24 hours, and has a wide selection (including stuff like chipboard). The ‘go to’ paper for letterpress since I’ve been interested has been Crane Lettra.
Metal plates are more expensive, but very nice to work with when circumstances allow. In one case, a wood backed magnesium plate was warped Sterling replaced it with a metal plate within 36 hours. I’ve used their wood and metal backed plates and have been happy with the turnaround and quality. However, when I do need metal plates (usually because a client wants to keep the plate as memento), I’ve used Sterling (based in London, but with a Kitchener office). Given the size of runs I do, I can’t really justify magnesium plates too often. When there have been issues, they’ve been incredibly helpful (even as much as noticing spelling mistakes when they pulled a proof of the plate, calling me to ask how I’d like to proceed, etc.). I email them plate-ready PDF/AI files, they make the plates in a day or so, then mail them to my house with tracking. Montreal-based That Sky Blue has been wonderful to work with. They are hard to find if you’re not part of the industry (at least I found it difficult) and there is a wide variance in pricing. I’m new to printing (I’ve only been printing for about five years - and certainly not in any professional/high frequency capacity) but have learned to cherish Canadian vendors of letterpress supplies.