You'd need a set of the corresponding Purdey bases, or a genuine rifle with them already fitted. The front ring would also need repairing back to its original configuration, although that would not be too difficult. But without those bases.......... I have had both bases & rings made in the past - several small batches - but have none at the moment, I'm afraid.

I don't know precisely how NZicon prices compare with prices in the UKicon, but over here even with the work needed on the front ring it would probably fetch at least 1000 GBP if not more. I do not know what effect on sale just at the moment the 'Covid-19 Factor' might have though.