The Omega Boutique in London will be happy to sell you a genuine Omega leather band to fit your watch. Should start somewhere around GBP150, maybe more.

First thing you need to do is measure the gap between the lugs. Most of these watches take 18mm wide straps, but this can sometimes vary.

I can suggest several eBay sellers, but many of them will not ship outside of the USA, as there are worldwide regulations called CITES that severly restrict imports of certain exotic animal hides across borders. Most domestic sellers just don't want to bother with the paperwork on a low cost item like that.

eBay UK should have you covered and I'm sure some members based there will have some suggestions for you.

Good luck and please post pictures!
gatorcpa

 

I've bought a few Hirsch straps and although good quality I found them stiffer or less supple for some reason, I tried a Hadley Roma and was extremely pleased with it, just a very simple black calfskin which does the job nicely on yellow gold.