Look at the NWSL offerings (North West Short Line). They have a wide assortment of for O Scale wheelsets with both needle point and square axles, and some variety of axle lengths. My LHS stocks a bunch of them. P&D Hobbies, which also has a website.
If the train shows were still allowed, I would suggest attending a 2 rail one and looking for some old Walthers wheelsets. They used to make them with blunt ends also, but not anymore in O scale.