Here are my candidates so far:
98935A817 3/8-12 lead screw 36″ 2G (McMaster)
This is $5.00 but that’s at McMaster which I think is useless as they wont ship to individuals in Canada. Their competitors are Reid Supply Company, FastenalW.W. Grainger and Manhattan Supply Company (MSC) but I wonder if this can be found locally.
A quick Web search found a supplier in USA.
I’m supposing we need a ball bearing with a 3/8″ inside diameter. VBX has them 10 for $24.95 or $2.95 each. In fact, I see a lot of 3/8 inside diameter bearings at different prices. I don’t know the differences yet.
3/8-12 Delrin AF nuts. I found them on ebay which looks great. They are about 5.00 each plus shipping.
I’m still working on that. The Nema 17 motors I got in China have shafts that measure around 5mm. 3/8″ is about 9.525″.
1/2-10 sized rod and nut might also be worth trying.