I need to make some spacers on a 5/8" axle shaft and I'm thinking if I could just buy a steel or even pvc pipe with 5/8" ID or slightly over that will be the easiest solution. Is there a standard steel/pvc/conduit size that I can get from the getting spot what has a 5/8" ID?
Depending on "how much space you need" and budget, purchasing "Plain Sleeve Bearings" might be the easiest way to get this done well if you lack tools to make your own. Such bearings are inexpensive, widely available, and come in many lengths and outer diameters with a bore that fits your shaft well.
Closest (larger) common thing I find is 3/4 PEX at 0.681 but that may not be "tough enough" - alternatively a steel tubing supplier (metal shop) may have more size choice in "not hardware store/home center" product.