Look for some available planes of a similar size. The Tupolev 204 is very similar to the 727 for speed, fuel use, range, etc. Takes a little longer to turn, carries a few more pax, and is significantly cheaper to maintain. It's available new, and you'll get the first one 3 months after you place an order. There are a few in the used market too. The MD-80 production line is more or less empty, and it's relatively easy to find used. The MD90 line is booked until mid 2000, 734 to late-2000, 717 line is empty now. All of those planes can do a similar job to the 727s & BACs you have currently. none are as good as the a320 or 738, but as you've noticed, those 2 are very hard to get hold of. You can't keep replacing ancient 727s, you need to work out which fleet you'll replace it with, and then do it.