Hi and welcome to CoffeeSnobs,
Non pressurised baskets are made by Krups and Saeco. Look up the service agents for either of these brands in your local yellow pages and take your portafilter along to the nearest....
They should have "normal" baskets which will fit your machine. As you know you will need a good grinder and the Iberital you mentioned will fit that bill.
With normal baskets and the grinder you should get really goods coffee.
If you need any help have a read of the posts here or post any questions you may have...
Enjoy your journey!