1997 Jeep Laredo Noisy belt

My belt was fine with no squeals, until the alternator went out. I had a well respected (and expensive) mechanic replace the alternator, and immediately the belt started squealing. They then replaced the alternator with same model because the spacing of the original pulley was off, but it still squealed after replacement. So I then replaced the belt myself. Didn't help. They suggested I replace the idler, so I did and that didn't help. They suggested I replace the tensioner pulley, so I did and that didn't help. No they're saying to replace the tensioner itself. Should I replace the tensioner, or should I try a different alternator? I'm thinking this is simply a mis-alignment issue, and perhaps this model alternator doesn't align properly with everything else. I hate to spend the cash for a new alternator when I've already got a new one in there.