Unfortunately, I don’t own a 3D printer - but I got a friend to do it for me. @InfamousTuba is correct - it’s from here: https://www.thingiverse.com/thing:5187271
If you follow the instructions, using 0.35 needles which are 75mm long, you’ll need to ‘trim’ about 3mm from the copper handled end. Reason is that the position of the retaining disc on the stirrer is set to a specific depth (which holds the needle from sliding), and therefore any longer in the collar wouldn’t allow it to ‘sit’ in its place. All needles need precise trimming, however if you get it wrong the only issue is a little ‘wobble’ in the structure. But me being me wasn’t happy, so I ended up electrical taping my one to secure nicely.
I found this size needle very hard to find too. So if you’re looking, the only place I could get them from was an acupuncturist/pharmacy/medicine type shop in Camden.
Defo use this template from the link above.
Message me your address, and I’ll send you some needles to go with your printout. And if you’re feeling generous, post out one to @DavecUK and I’ll include a set of needles for him too.
Always happy to help out fellow coffee guys ;)