You might want to check out the coffeeparts website.
I used to have a La Pavoni Espresso machine a while back, and noticed that the portafilter was the same as the Saeco ones.
It was pressurised as well. So you might want to take some measurements of your portafilter, and check out the coffeeparts site, the la pavoni ones might fit.
Far better to try and get these things locally, not worth it to order them from the USA. Shipping costs are just not worth it.
Just out of curiousity, why would you want a non-pressurised portafilter? When i was using the La Pavoni, I did not have to pay too much attention to the grind, and tamping, its a very forgiving way to get your espresso shots. Only problem was the ocassional "explosion" when the basket was overfilled, or tamped too hard.