Searching in the UK it does look as though there are just the Librands Sports Exhaust, which is cat back although there is a possibility that
Williams may do one now; I know they have been developing them for other models.
The other option is just to replace the existing silencers with the Sports ones from
Melvyn Rutter which is less expensive and the route I went down. Those give the exhaust a nice burble at low revs but are not excessively noisy at high revs.