Thank you both for your replies. The spindle is indeed 131 mm without the threads. Just for fun, I measured it again and with them it hits a whopping 156 mm length!

The longest BB that I managed to scrape up is a VP components with a 127.5 mm long spindle. I eventually bought it and installed it today, and it fits quite well too, actually the left crank still has plenty of space around. This round of renewal & repairs is still unfinished so I only had the chance to try the bike out for a few meters... I'm keeping my fingers crossed.

On a sidenote it occurred to me I just assumed the lower quality BBs have 9 balls when instead mine only had 7. Talk about cheap! as I said in my other thread, this is a 20 yo road bike but still..?

PS: removing the right cup was an adventure in itself, kudos to the late Sheldon Brown for his wonderful site and all the people who are keeping it alive.
PPS: most of the shops in my area are small and seem to be one of two types: in the first one the owner also does repairs and is seemingly always busy fixing an old bike in for trivial repairs. The other is more upmarket, and the owner appears to be constantly intent on selling an expensive bike or two. Either way they don't seem to be interested in wasting too much time with me, and I ended up buying most parts in a chain store.