Retro Computing Shack sell them. They are a UK eBay seller. He isn't listing any right now but contact him through eBay and I am sure he will have what you want.http://myworld.ebay.co.uk/retrocomputershack/
His RGB scart leads are great quality. I have two of them, one for the ST and one for the BBC Micro. The best picture quality ever on my cheapo LCD telly.
Ah sorry, just read you want to buy in bulk. I'll get my coat...
Too many retro computers here: 1040STfm, Mega4, Ultrasatanx2 , Amiga A500, A500+ and A1200, Acorn Atom x2, BBC Micro, Electron, Spectrum 48k x2, +48, +128k, QL, Oric Atmos, ZX81, Memotech MTX512, Amstrad 6128 x2..