Well I appear to be the first with this idea. When I first saw the bubble shield I thought it looked unfitting, so I opened the particle editor and got to work:
FOR DECENT-FAST COMPUTERS ONLY
Due to constant TF2 updates that break the mod, I am going to cut off support for this, but instead tell you all how to get the manifest to function correctly.
-First off, you will need this program to access the Team Fortress 2 cache.
-After GCFScape is installed, open it, and open the file named 'team fortress 2 content.gcf' located in "C:\Program Files\Steam\steamapps"
-Direct yourself into root\tf\particles\ and located the file 'particles_manifest.txt'
-Open it up, and add in: [ "file" "!particles/turret_shield.pcf"] (without the  ) into the file, but before the bracket at the very end. It must be the last listed one.
-Save the newly editted file in C:\Program Files\Steam\steamapps\