the shield is made out of like 20 models the last time I heard about it
so good luck on that
now so I don't sound like a cunt and not write anything useless, I used a hex editor a while ago to edit one of the .so files related to the engine that held all the models of the weapons and stuff and replaced every single model with a HD one without using any single resource more from the 512 limit than there already were, you can probably do that there, but it's probably not the solution you're looking for
edit: I found this, look inside the source
Some model changer plugin that supports shield