I would like to build camera with A4 sized negative (21cm x 30cm) or something near that size. Only proble I have is the lens.

Negeative material will be cyanotype-paper, which means that pinhole is not an option. (Few months explosure is too long even for me)

So I need a lens with following:

1) Reasonable fast lens (One day explosuretime shoud be enough)
2) Focusing (or if not possible then allways focused to infinity because I would not like to construct Bellows)
3) Large FOV. I just love wide angle pictures

Reasonable Vingetting or slight softnes are not problems. I do not need extreamly sharp images.

What kind of lenses I could use with this camera? Is there a cheap way to get any lens just for my needs?