replacement shifter mine wont stay in 4 low lock

Here is a site that should have any parts you need for your car or can get the part you need: http://www.laceyusedautopartsinc.com/inventory/retail.htm You need to put in more information about your car to find the part

I have a shifter that would not stay in gear as well so I unbolted the shifter which was full of mud and debris. Disassembled and cleaned out well and regreased unit and now works fine.

Have you tried LMC Truck? Their phone # is 1-800-LMC-Truck, or go to LMCTRUCK.com They have just about everything you need to fix, build, or rebuild most chevy and GMC trucks, just tell them the year and make and what you need. They'll send you a catalog.