I have a verbal order in to a vendor already. As soon as payment is received for an eBay item I'll even put a deposit on it.
Couple notes based on above comments. Like Louis said, Patton was the main detractor of sandbagging. As an old cavalryman he valued mobility and aggressive tactics. There was also the wear and tear on the tank. HOWEVER it was Patton's Third Army that standardized a STEEL armor upgrade. Due to the limited production of M4A3E2 "assault" tanks (often called "Jumbos"), the Third Army authorized workshops to take steel plates off wrecked Shermans and use that to "double up" the frontal armor on several hundred M4A3s in 1945. There were three problems with the Shermans' protection; ammo stowage (addressed in later "wet stowage" Shermans), high-velocity German guns (thicker armor needed - addressed in a limited number of tanks) and the proliferation of hollow-charge AT weapons (Panzerfaust,etc) which was the main reason for the sandbags. A sandbag isn't going to do much against at 75mm or 88mm AP shot at combat ranges, but was thought to help break up the warhead jet from a Panzerfaust. Note that although Third Army was on record as against the sandbags, Patch's 7th Army not only didn't care, but their 14th Armored Division is the outfit that had standard metal framing added (like the new K&C model) that held sandbags on the upper hull and turret. First and Ninth Armies didn't seem to have a policy.
As far as the muzzle brake of 76mm guns - the M4A3 76W could have three different guns - 76mm gun M1 had a plain muzzle, M1A1 had the muzzle threaded, but the threads were covered with a protective collar, M1A1C and M1A2 had a muzzle brake fitted. Any of these guns could appear, so Andy's 76mm tank is fully correct.
Gary