For my 582 I was recommended to get mine from ASWO however I had to register with them and so on. I tried their belt on my 582 and it seemed to work well. Nowadays however I have installed one I bought directly from the Nak master Tom van der Hoff in Netherlands.
The ASWO link is the following, however I don’t have at hand the direct link or dimensions of the belt I bought from them but I can get it for you.
https://shop.aswo.com/aswoShop/start...es?storeId=509
Cheers