When I was a young engineer (in the 1980s) the Company I worked for was buying from Plato all the tips for our Weller ad Philips irons. The rep told me that Plato had the patent for iron coating the tips, and they were the original manufacturer of the tips sold with many name-brand tools.
I don't know if this is true (he was a sales rep, so not at all trustful), but I must admit the the tips were indistinguishable from the original, both for performance and longevity. I remember they were not cheap.
Another Company, OK international (
OKi), the manufacturer of Metcal and Oki soldering station, sells spare tips for a lot of soldering and desoldering irons, including Weller and Pace.
A limited selection is available on their Italian site:
http://webstore.okinternational.it/shop/articoli.aspx?idArt=601Note that prices are for 10 pieces, bot excluding (the one in bold) and including VAT (iva inc.)
They sent me a catalog with tips for other brands, but I can't find it now.
I was unable to find the corresponding page on their international site, but I think it is there...I did not test them, but I'll do asap.
After saving the post, I found their international webstore:
http://www.okinternational.com/storeI see that spare bits are not available in all coutries..