For decades Metal Lathe Accessories has been offering kits of castings for making useful accessories for the metal lathe. I’m considering buying their Steady Rest kit as the price for a used/import steady rest for my South Bend 10K lathe is three times as much ($150-$200). Other useful kits that stand out are the Die Filer, Milling Attachment and Quick Change Toolpost, but everything they offer looks useful.
While the amount of work needed to make these kits into useful accessories is somewhat hefty, the kits are a great way to learn metalworking techniques while adding to your shop. In my years of following internet discussions I have only heard glowing reviews of the quality of the MLA castings, drawings and instructions.