As I recall, true Osaka-ben substitutes 〜へん for 〜ない (as opposed to Osaka-fied Tokyo-ben, which changes it to 〜ねぇ), however for a moment tonight I got stuck on what to do for ない on its own (e.g. 時間がない "I've got no time"). Using へん on its own sounds off, and I seem to recall hearing あらへん a couple times in that context, but I thought I'd check here and see if someone else knows for certain.
While we're on the subject, thought I'd also inquire as to how it came about. My best guess is that it evolved from 〜ません to 〜まへん, then shortening to simply 〜へん, but that's just a guess.