Can't say enough good things about Old Britts (
http://www.oldbritts.com/ob_main.html). Very good and reputable. However, I do business with Raber's in the SF bay area as well, don't hear as much about them, but really good folks to do business with (
http://www.rabers.com.) Also deal with RGM (
http://www.rgmmotors.co.uk/categories.aspand) and Norvil (
http://www.norvilmotorcycle.co.uk/) in the UK, both good, have had returns, and what not no problem. Bought from Clubman in Connecticut (
http://www.clubmanracing.com/nortonexhaust.php) and Walridge in Canada (
http://www.walridge.com/), both fine. There is this place (
http://www.britcycle.com/) I have asked to get their price list about 5 times and they ignored me, for whatever the reason, so fine. There are specialist guys like John Bould that do fork upgrades, I got those, he is good to work with. Madrass makes some nice upgrade parts. So does Colorado Norton Works (
http://coloradonortonworks.com/). Hi performance parts here (
http://www.jsmotorsport.com/.) There is a place in Tucson AZ called AMR, way scaled back but do some upgrades (
http://amr-of-tucson.com/) I have not dealt with them but a friend of mine says they do good work. Someone mentioned Andover Norton. Have bought EBAY parts from this place (
http://www.baxtercycle.com/) As you look thru posts here you can glean what you need depending on what you are looking for, there are many more places these are the ones I either buy stuff from, or lust after their very cool items I can not justify needing, or can not afford. I am trying to control costs (I am rebuilding a basket case) so I do a bit of comparison shopping, and I also like to patronize all sorts of places never know who will have what and good to have relationships. Make sure you understand shipping details, can be a real cost adder or deal maker. Hope this clickable links get you some good leads. Get a parts book, best way to search most sites. Also, need to know parts formats, some sites like 06-6972, some like 066972 to search. Good luck.