Well, the Denix Thompson is - to my knowledge - the M1928 version. It has the charging handle on top instead of the side and the upper receiver is said to be "blockier" than the receiver of the M1A1.
I have, however, seen at least one Denix Thompson modified to an M1A1 version. This way, it might work. But that might be more work than the result justifies.
Your best bet would be to find an airsoft Thompson M1A1.
Cheers!
Roman