You'll not find a genuine Sharp breech other then by buying another sharp to break for parts.
You can get the Puma manufactured copies from Chambers, they are barreled in 177.
The (plastic) front sight and silencer adaptors can be had from Chambers for £15 or so, but they only come into stock once a flood and they sell out almost instantly - log on an set yourself an email alert for them. Alternatively check tinterbay for one of the early custom made alloy ones, they come up from time to time but expect to pay north of £50.