Interview attire for women...shoes!?

I have a job...a boring one but b/c of education budget cutbacks the company I'm working for might go out of business by the end of this year. I'm asking so I will be prepared ahead of time. I have a nice looking outfit (tailored & professional looking but in light pastel spring colors) BUT my problem is footwear. I have very wide problem feet so I can't wear any type of heel. As for flats...most are too narrow even in wide width. ...so all I'm left with is crocs (the unisex ones...all women's styles are too narrow) and doc martens, both of which are very casual shoes. I have very limited income and lots of bills so my budget for "dressy" shoes is extremely tight....like less than $100. Ok...any ideas? I know crocs and doc martens would look hideous for an interview but would these be acceptable for someone like me?