You might want to try Battle Orders
Battle Orders Ltd Battle Orders
They are based in Kent & could advise you based on the legality of what you want in the UK. Alternatively British Knife Makers Guild have a really wide selection & have contacts with custom makers The Official British Knife Collectors Guild ... Hunting Knives, Collectable Knives, Rescue Tools, Folding Pocket Knives and So Much More

I noticed that you also asked about gun laws in this country. Can I respectfully suggest that you are very careful? The legal & political climate in this country is not friendly at the moment for lovers of the sharp & shiny. The basic design of the knife you are looking at is known as a punch dagger & is very illegal. Of course. if it's not sharp, you might not get trouble from the rozzers. They could still see it as a knuckleduster & that is illegal too!