Old Moen Trim Valve Replacement

It's a Delta not a Moen. Sorry for the confusion. I am having a problem. The shower trim shown below is old and leaking a bit. I am trying just to replace it or rebuild it without doing any major plumbing like soldering or removing any piping. Is this even possible? I can't find a model number anywhere and I cant seem to find a direct replacement anywhere. The drop in vale doesn't seem to be used anymore and it is nearly impossible to find anything that I can just remove and replace without tearing out the tub to replace this one piece. Any help is appreciated. Thanks in Advance.

http://i1016.photobucket.com/albums/af284/smsaddict/IMG_20150904_174115359_zps59gm5c4m.jpg

http://i1016.photobucket.com/albums/af284/smsaddict/IMG_20150904_191127470_zpssq8yo9p3.jpg

http://i1016.photobucket.com/albums/af284/smsaddict/IMG_20150904_191141372_zpslqiuosta.jpg

http://i1016.photobucket.com/albums/af284/smsaddict/IMG_20150904_112305805_zps6zz0zqz6.jpg

That is a Delta Scald Guard cartridge. Look for scald guard trim.
I had some hits for handles and cover plates on Amazon.