There is good news and there is bad news. The bad news is that, unfortunately, these processors are so old that we don't have them around anymore. We typically recycle our old stock.
The good news, is that I found some from buycheapr.com for $25 - $30. They aren't in a box, but they would be the same processor that did come in a box. You alo might want to check to see if your fan is working properly. If it isn't, your processor may be shutting off due to overheating.
Good luck and I hope you can find a solution to keep your system going.