In the UK Rapid still do it : https://www.rapidonline.com/Catalogue/Search?Query=60%2F40%20solder
I think their EU sister company is Conrad.
Rapid need a business account to buy lead - I rceently set this up for this purpose after buying from them for 20+ years. I don't recall what they needed to show I was a businees but don't think it was much.
I know they sell Conrad products via Rapid UK but not sure it works the other way.
Aliexpress or Ebay is likely to be your easiest bet.
ESR Components in the UK are aimed mainly at the amateur and they sell Cynel 60/40. I can't imagine they sell much to businesses. There's a warning about how it's only for personal use and must not be used for projects for a third party or sold. I don't know if they ship to the EU, or whether it might be seized as contraband. There may be similar outfits in the EU.
I've never bought from Rapid. I do buy from CPC and Farnell without a business account, and I haven't got the impression that there's a restriction on leaded solder. I've just accessed CPC and put a reel of 60/40 into the basket and went to checkout and no warnings popped up, but there and again, I didn't actually try to buy it.
I tried unleaded solder and didn't like it. When the talk of a ban on leaded solder started about 20 years ago, I stocked up. It turned out to be not really a ban because there were so many exceptions for avionics etc. Basically it wasn't to be used in consumer products, which I suppose is fair enough. To be honest, I haven't had to buy any leaded solder for many years.
I've been happy with what I've bought from Aliexpress, but I wouldn't buy semiconductors from there and solder would be a last resort.