Hello and sorry for the late reply, I didn't see your answers :}
Hazlomanualidades, I had a look at your website, but I couldn't find steel hooks, only aluminium. Maybe I didn't look in the right place? (my spanish is not very good, lo siento!)
Marmalade Eagle, I thought about ebay and will keep having a look from time to time, who knows, but so far I also only saw aluminium hooks that were more than 3.5 mm... And what I'm looking for is really steel hooks.
Anyway, thank you very much to you both for your kind replies !