There's someone on ebay based in Weymouth who lists camelbacks kbalstmetalworking 12" currently come in at £150 unmachined
They are apparently cast by someone called KJ Metals.
I've have no contact with either firm.
There was also blacksheepuk2015 on ebay, who, as I recall, was a machine reconditioner who had some surplus castings up for sale earlier in the year; I believe he'd had some cast for himself and added a few extras to the batch. I think he said that those would be his last batch.
That might well tie up with Pete Cordell's comment above, which points to H.R Lamb and son; machine tool reconditioner and straight edge manufacturer..
Bill
Edited By peak4 on 08/11/2020 12:30:39