I found some 4-48 ,25 on eBay stainless steel with slotted head, Ordered 4 to see if they work.Part of the problem I've had is that the screws have been installed poorly by Crosman. On a 2400KT the screw was rounded out by Crosman, obviously over tightened. Actually that 2400 was a mess -- the bolt wouldn't open, there was brown glue like substance in the breech. The bolt handle had been tightened/locktited to the point of needing a wrench to remove it. The spring adjustment for the trigger was tightened to the max. I had to strip it down and clean it before I could shoot it -- kinda took the joy out of getting a new toy.
Here is the link: http://www.ebay.com/itm/SS-Slotted-Breech-Screw-for-a-crosman-2240-2250-1377-1322-22xx-13xx-/321104265172?pt=LH_DefaultDomain_0&hash=item4ac34e3fd4