Ive got a Café Roma, and yes, Ive had issues with it. BUT, rest assured that the Breville customer service person I spoke to this morning agrees that my machine sounds faulty - and Ive heard about and seen plenty of success with others Café Romas.
I believe that if you speak to Breville, they will suggest the Bar Italia baskets (part numbers ESP2/41 and ESP4/51 are the "1-2 cup" baskets for both models of the Bar Italia - I have both and they are almost identical and hold 16-18g ground coffee. The ESP4/51 (newer version) has a slightly better ridge on the basket rim which should translate into a better seal). If your machine is working properly, these baskets should seal reasonably well against the group head. Some people have found that they dont really seal that well though.
There are also Krups baskets which fit the machine [part numbers: 0907163 (double) and 0925592 (single)] but I have also heard people complaining about the quality of the seal with these baskets.
Im not sure which baskets youre referring to at CoffeeParts.com; I havent been able to find any that would fit the CR, but I might be wrong.
I think the best option (if youre game) is to de-pressurise the normal double pressurised basket, either by making the "pin hole" bigger, or by using an angle grinder to take most of the bottom layer off (leaving a rim around the edges so that the top layer is held in). There is a good thread on how to do this here: http://coffeesnobs.com.au/YaBB.pl?num=1168768543/0. The advantage of this is that the basket is specifically designed to seal against the group head with that seal... so it SHOULD do so.
However, before you embark on either of these upgrades, youll need a good grinder! The pressurised basket is actually likely to help you make BETTER coffee than unpressurised baskets if youre using a grinder which produced grinds that are uneven or simply too coarse. Once youre using unpressurised baskets, you need everything else to be right - grind, dose, tamp pressure, tamp evenness. This is, of course, what all baristas have to be able to control so its worth practising. I certainly havent got it right yet (not helped by my poorly-sealing machine... but a poor barista [exclusively] blames his tools :P).
Others will be able to advise you better on tampers, but I know that the CR has smaller baskets than most tampers so youll have to take a basket shopping with you... I think theyre 51mm or something. Tampers that are worth using are generally $50-100 (ie. half the price I paid for my Café Roma!). Which makes it tempting (for me) to make one myself.
Hope thats helpful.