There used to be a vendor that stocked aluminum blanks in one or two configurations but I dont think they still do. You can turn aluminum (and brass) blanks on a wood lathe with the proper technique. However, drilling a hole and gluing a tube into a metal blank seems redundant, and the Inside diameters of the tubes in most kits are not standard drill sizes. So you drill it over sized and glue in the hardware. Most people who turn to metal end up getting a small metal lathe and can then make the blanks and the Hardware themselves. If you dont want to invest in a metal lathe, (it isnt cheap) ask if someone will make you a specific set of blanks as you want or need them. Someone will make them for you. Exotic blanks does still sell steel Rebar blanks although Im not sure for which kits.