Trying to order the plastic flaps that are usually stapled to the inner fenders to block off the engine bay from the road but cannot remember for the life of me what they are really called.

Thanks

Not plastic. Rubber.
And they're called aprons (although the AIM simply calls them seals). ;)

Some of the vendors refer to them as A-Arm splash shields.
Ricks, Page #183 ( for a first gen).