Robbie, I'm working on repairing a WLF for a Mamiya C-33 and have needed several small screws, so I know what you are going through. I'm new to this mini-screw thing too, so here is a bit of what I've leaned.
Your metric measurement of 1.5mm is probably a 1.6 mm screw (no argument on length). Metric screws measure about 0.1 less than their nominal diameter. Searching the internet on "mini screws" I found the site:
www.metricscrews.us and was able to order several screws from them at what I thought was a reasonable price. You might be able to find something that would work there. Also, another source for tiny screws is watchmaker suppliers, like esslinger.com, or jewelerssupplies.com. Hope this helps.