where can I get replacement relay/fuse box parts?

[GreenV8S]

The OE relay / fuse box on my V8S is made from a modular system of individual fuse and relay holders that are dove-tailed together to form a single big unit. The dove tails are very shallow things probably only 1mm deep if that. I'm looking for some replacement parts but I can't find similar ones anywhere. Any idea where I might be able to find them? (I know various places where I can buy different modular fuse boxes etc but I'd like to keep them all the same if I can.)

Thanks for any help,
Peter Humphries (and a green V8S)