Neil:
Tamiya has a couple of 1/48 Shermans, I believe an early one and either a later and/or a Firefly.
It seems to me that Monogram/Revell had a 1/48 Sherman with an M4 Halftrack, but thats been awhile, unless somebody has some to sell. They were rudimentary appearing, I did not see one "in the plastic", only an ad someplace. They also had 1/32 Shermans, but not what you need.
Aurora had a 1/48 Sherman years ago, probably a collectors item at this point.
According to the leaflet in one of my Tamiya boxes, the early Sherman is their kit #32505, and the later is #32523, an M4A1 (whatever that is).
Their U.S. Army infantry set is #32513, and there are two German sets, Infantry #32512, and panzergrenadiers, #32514.
That help?
Hey, I'm an airplane guy, but I always thought a couple of vehicles around them would look more realistic, not to mention figures.
Good luck and regards,