Ref 135-010 Omega Case.

I hope I'm in the right area to ask for information on my Omega Seamaster De Ville Cal 601hand wound non date movement with Arabic numerals dial. I bought the movement at auction and have been searching it seems forever to buy the correct Ref case, there was one came up for sale on Ebay last October but unfortunately I was out of the country and missed it, what was even more annoying was it went for £17. As temporary measure could anyone advise me of a suitable Cal 601 case that would be compatible with a dial 27.5mm.