Presumably you are talking about the clamp on the pipe side of the junction with the centre box.
I had this issue when the stainless steel silencers were fitted back in 2015. I designed a two piece clamp comprising 6 identical pieces of 2 mm sheet steel which could be welded together as a pair of half circle clamps with fork and blade style connections where the bolts go through. Every near half circle had a bolt hole in it but the three pieces comprising each one were offset so the middle section poked out one side and there was a gap between the bolt holes on the other. Classic example of design from my Over-Clever period but the intent was to produce something that could be made with hole saws and a drill by normal folk.
No great issue to make one for you, or send a copy of the drawings if you fancy DIY and know someone to do the weld together bit, but I can't guarantee the fit as I never made the thing to verify my drawings. On something that simple they should be right but...
In the event the exhaust place got clever with their gas welding gear and stuck a pair of L shaped brackets on the pipe sort of aligned with the bolt holes on the silencer box. Lots of exhaust paste stopped the leaks. Which barely made it to next MoT before I had to get clever with stepped suds to overcome the fit errors and stop the leaks properly.
With 20/20 hindsight I think they would have done better to leave the L brackets separate and loosely bolt them to the centre box before fixing to the pipe with a clamp and finally bolting up when the brackets were secure. I imagine a Mirkalor style clamp would be needed to clear the bolt heads. U bolt style would almost certainly get in the way and a jubilee style clip just won't be strong enough to pull the L brackets hard onto the pipe.