A DIY counterweight bar and weights are a fairly easy project if you have a lathe, a pillar drill and a few other tools. Could be an interesting little project.
The bar might have to be something like chrome alloy steel with all the weights hanging off. Possibly even go up to 30mm depending on how and what is attached at each end.
Large diameter stainless steel rounds are pretty expensive, smaller diameters could be drilled and filled with lead. Delrin could be used with lead slugs, they won't rust.
Attaching the saddle to the shaft so it doesn't come loose has various solutions, threaded in with a locking nut, cross pinned, loctite...
The main question, is it worth the faff in time and effort or easier to pay the 169 Euros.