You didnt get the Problem here Loveboy.
These 'bomb'-objects are script_brushmodels (in your *.map file) and they are compiled into the mapname.d3dbsp, there is no way to change them!
You can create you own maps and use the prefabs of these, but you have to compile them before you are able to play on your maps.
The only possible way to have other bomb-objects is to delete the original ones and spawn some xmodels, however these dont have any collision.
(faking collision with spawning triggers + setcontents)
You could also try to change the models of the script_models, but i dont know of this will work.