Shocking...
YSS makes a nice set of choices, Penski is in the game, Koni used to play, Hagon offers options, I believe that Olins has a set...
Keep in mind that the basic design of the Norton, as dear as it is, doesn't come close to modern suspension. The isolastic feature alone kills off much of the handeling potential. And don't forget that radial ZRs were only offered on the VR 920, that never made production. Also, when you feel a non-folding foot peg start to bite the tarmac, you better be tight on the apex or have good insurance.
Most Norton owners haven't changed their fork oil and wouldn't kmow what the term "sag" means, not an indicment, a fact.
If your Isos are new (and properly adjusted), your fork is tight and has fresh oil you can get real value in a new set of shocks, but you don't need to spend a lot, unless you like the look----What Iam trying to say, put bluntly, is that the only difference between Good, Better and Best is, mostly, price.
The Norton is a superb example of classic machinery, It offers the one of the smoothest rides in the industry (even now) and also offers a rewarding set of endless machanical challenges...