Apparently I just missed you. Heard that the parts are a ballast and counterpoise for the buoy you mentioned.
Seems that the cross-slide on the lathe is a bit sticky, but it does have a serviceable section in the middle. I can donate some used tool inserts from work if I find suitable ones.
You might be able to find stock like what you need for scrap price at Niemen Romukauppa (https://www.fincumet.fi/niemenromu/), or possibly get the whole thing made at Hellmanin Konepaja (http://www.helkone.fi/) since this would be a small job for them. Not sure if Hellman accepts walk-ins, but you wouldn’t be the first to try. The price shouldn’t be terrible so if they quote you in the hundreds it means they don’t have time. English could be tricky at these places. Young people usually speak it quite well, if you can find them…
All the best,