Post with Multiple Categories and Permalink's

Hey everyone

I am developing a financial advice site for a client and they have started adding articles which fit into multiple categories so when you view one the permalink category will appear depending on which category you were in at the time (if you follow me).

What they have asked me now is that if it it possible to select what category shows up on the permalink no matter what.

Any suggestions rather than custom fields? like a plugin or something that has managed to hide from from my Google searching.

One solution I have thought of it using the redirection plugin but that isn’t exactly ideal.