As others have said, there's a reasonable turnover of De Vere stuff on ebay. I agree that Odyssey are nearly always more expensive, but they have always had the items that I wanted, when I wanted them, not when someone else decided they wanted rid of them
As a guide, in Nov '09 I bought the following from Odyssey:
Recessed lens panel for 40mm (and wider) lenses - £35
35mm neg mask - £25.
Just as an aside, I found out when talking to John(??) at Odyssey that there are two recessed lens panels - the 'slightly recessed' one, which seems to be for lenses >=50mm.
The other one is the sunken lens panel, for lenses <40mm.
Hope this helps!