Link is broken. I don't think the finder.cfm link is supposed to be shared. Anyways, I found the correct (I think) lenses on http://surplusshed.com http://surpl

Link is broken. I don't think the finder.cfm link is supposed to be shared. Anyways, I found the correct (I think) lenses on http://surplusshed.com http://surplusshed.com by going to the lens finder link and looking up double convex, 40mm focal length, 25mm diameter lenses. $4.50 each, which is pretty good. EDIT: The article says to use biconvex lenses, whereas I looked up double convex lenses. The surplus shed website has double convex as a separate search option as biconvex, but wikipedia says they're the same thing? If someone has more knowledge about this I'd really like to know if they're at least "close enough" to use, since I couldn't find any biconvex lenses on the website of the correct parameters.