Theres a WW1 mod being made now, but until then I think you may be closer with just WW2 addons.
The BAR was made late WW1
The Thompson was made in 1928
The Garand came into service in 1936 I think, but if you could find a springfield rifle addon, you could use that.
The .30cal was used end of WW1
Forget the Bazooka, because that was made in 1942.
As I said before, the Springfield scoped rifle was made way before WW1, so that could be used.
So you have quite a good, downloadable armoury there.
Have you got a picture of what the troops looked like, so we can see what we're looking for?