I've still got four that I use for all my feeder fishing on big windy venues but sorry I wouldn't ever part with them. From memory two came from Bob himself when I was fishing Wilstone years ago. I then got another four from Swale Angling before it shut down and gave two away to a mate ( I'm not 100% sure but I think I recall Mick Dinnigan, who worked at Swale,had purchased the patent?).
You could make something similar but the clever bit ie the free running, quick release plastic head would be difficult to replicate.
I do recollect reading on a forum someone asking a similar question. He received a response from someone who said he was Bobs grandson - might be worth a Google search?
Incidentally does anyone know what became of Bob, he was a lovely bloke and a good angler who invented some great bits of kit?
Good luck with the search.