Any ideas on how my characters could plausibly get their hands on two or three police uniforms? They have limited time (I'd like them to have them within about three days of deciding they need them) but a lot of money at their disposal and a quite senior police detective on their side. However he is under a mild degree of suspicion and very scared of getting caught though (and I don't want him to get caught either, or it to seem like he should have been caught) - he won't want the authorities to think, "So, uniforms go missing from Detective X's precinct and next minute criminals dressed as policemen are committing a rather high-profile crime! Hmm..."
Googled - "stolen police uniform/s" "stole a police uniform." Came up with a case of people stealing uniforms from a dry cleaners, which is definitely a possibility, but I'm not quite sure even how you would go about doing that. The uniforms do need to fit, too, though they could probably spare enough time to make some basic alterations.
EDIT: Re some of the comments, yes if they can do it without committing a crime, so much the better. Really I just want to clear this up as quickly and economically as possible ("The uniforms were in a bag on the chair, they'd got them from x by y means.") I suppose a lot of my trouble is not really understanding where police officers get their uniforms from normally. Wouldn't suppliers be cautious about selling to just anyone?