Hi Domenic
ioptron weights for ieq45 are well made with brass locking pins and approx 28mm bore. They are cheaper than others.
https://www.ioptron.com/product-p/8027-05.htm
If you can't find any partners and you only want 2, suggest you buy a couple of those and get them bored by your fitter to 31.75mm?
You would be surprised how much steel costs and how much time it takes to machine and thread tap. A friend of mine did a quote for an IIS member about a year ago just as a favour to me. He wanted 2 x 200mm diam, 20kg counterweights large bore. The steel alone cost price was about $200. People who don't machine metal frequently don't understand how long it takes.
I recently made 6 small custom threaded T nuts for a finder with 3mm metric thread inside and stepped 6-10mm outside diameters. took me 3 hrs to make 6. I did it in the workshop with professional fitters around. I asked them how long it would take them and they said they might do it slightly faster but not much. Tapping a long thread in a steel counterweight for the locking pin is a very time consuming job.
Joe