MacBook Pro power adapters are becoming increasingly hard to find as Apple is apparently pulling inventory and not releasing any more until it has new versions available. It would seem that the motivation is avoiding possible problems cause by flawed adapters, and should end as soon as the new model is ready.
The online Apple Store lists the MacBook Pro's 85W power adapter as shipping in two to three weeks, and all major retailers are also listing the product on backorder. The first thing that comes to mind is that there might be something wrong with the current stock, especially considering that there have been quite a number of reports about problems. AppleInsider reports that Apple is not putting out any more adapters as they intend to release a 'redesigned' model. While there doesn't seem to be anything in particular wrong with the current stock, the new design is intended to put a stop to the various problems encountered with the MagSafe power adapters once and for all.
Of the problems reported by users, three are the most common: the first would be the tendency of the thinner adapter cord to heat up and become frayed near both ends; the second is the way the springs inside the MagSafe connector spring back into place, which can result in a faulty connection; the third is the LED indicator which will flicker even if the adapter is charging the MacBook Pro properly.
While none of these issues has been big enough to warrant an updated model, the combination of the three might have pushed the company towards a better model. There is no further information about the upcoming models and what other improvements they might offer, but at the very least we can expect these issues to be gone once and for all.