hi joshua,

if you have a digital caliper (sometimes on sale at harbor freight for $10), measure the diameter of the arms that you have. a 3 foot stick of 1/4”-1/2” cold rolled steel rod is usually less than $10 at home depot, or available from mcmaster carr +shipping. it’s easy to cut and file and you will have more than enough for longer arms. if you want tighter tolerance on the rods, or need metric, get drill rod from mcmaster carr, or wherever you can source it locally. it comes un hardened so it is easy to cut and file

good luck

barry