So I got a Robin Mather...

I'm a bit stuck on bar/stem combo at the moment as I really like my current Deda bars but they're oversize and 460mm wide and I can't find either a quill stem that would work with them or some standard size bars for a quill stem the same shape so might just have to use a quill adapter and use an Ahead type stem.
Thoughts, suggestions?

I think I saw this on the bay, is it an audax(ish) frame?

i'd either look at those bonti bars or an adapter in the short term, and then if you like it and want to keep it, I'd probably drop him (or another builder) an email and see if you can covert the forks to an ahead. TBH there looks like there's enough space with all those spacers just to clamp around the threaded part with a shim.

..or many purposes such as velocio's nodder hybrid 29er shopper...

Says you with the nodder sized headtube!

;)