Goldmund Studietto

Contact Bill Thalmann at Music Technology repair center. 

You can measure pivot to spindle distance on Studietto to figure out your limits, do you have spare arm board ? When you know PS distance you can choose whatever tonearm that can be mounted within this PS distance. Instead of pivot point you can use the center of the hole made for tonearm on your arm board (this is where the pivot of the arm must be when you will buy the tonearm if it's conventional design).  

But more important is tonearm+cartridge matching, than tonearm+turntable matching when you can physically mount the arm within manufacturer PS distance.

Probably you can use Fidelity-Research FR-64fx tonearm, this is a great arm!

I had a Studio with the T3 which was the best sounding combo, once I figured out what cartridge to use (mid compliance, heavy).
I remember hearing it sound ok - if a bit mushy - with an Alphason 100, and much better (more extended) & crisper with a 12 inch (SME 3012 I think- if not, it must have been a Jelco, not sure). Someone I know tried a Rega 300 which was a hassle to set up correctly (no height adjustment, etc) but it sounded OK.
Had to sell for financial reasons, otherwise I’d had held onto it. Sorry, not much help here...

Don’t have an arm. Looking for arm recommendations 

find effective mass of the arm and then you will see what cartridge is compatible 

How come you weren’t very happy with it? 

I had a Goldmund Studietto thirty years ago. It had the Goldmund T-5 linear tracking arm. It was the best looking table ever, but I was glad to sell it. I don't remember which cartridge I used with it, probably a Grado, but I could never get it to sound the way I liked.