I just bought these in tan for work. Yes, I know its M&S but they are wide fit and comfy! They look lovely on with skirts and trousers. Some others in the contemporary footglove range are nice too. Or you could try DUO - there is a sale on at the mo and their shoes are lovely, last forever!
I've seen loads of people wearing 'Toms' pumps recently. Not sure if they're any good? Have a similar conundrum myself but don't want anything too open, as after a day in Central London my feet are black with dirt in sandals.
There are a lot of summery toe hiders in the Toast sale here esp the Paloma sandal, Pascale heel and Tabitha Oxford, which all have a design that to some extent will let the hidden toes breathe. The more muted colourways might be more work appropriate. I am biding m time however to see whether there might be further reductions.