My Seiko A159-4000-G needs a new seal for the battery cover. I’ve measured it as 15mm dia but is that correct? Also is it a flat or round profile O ring?

I’m having problems finding anything near that size anyway! Does anyone know a UK site where I can get one or two?

Look here Ash55 :
http://www.ebay.com/itm/900-pcs-O-Ring-0-5mm-Gasket-12-13-14-15-16-30mm-0167-/270752130455?pt=UK_Jewellery_Watches_WatchAccessories_SpareParts_SM&hash=item3f0a15a597

I bought this set so i can always choose the o-ring i need, 12-30mm diam. ,guaranteed to fit nearly every lcd watch.
You should take 0.5mm thickness, as my experience is that with thicker o-rings the battery hatch will not close properly.
A must for every collector, and not too expensive imo.