S & S have some Deep Wading trunks for Shermans & M10s but NWE pattern. They may do for your purpose. Alternatively pester them to make them to a different pattern, as they already do the wooden applique armor used on USMC Shermans. http://sandsmodels.com/
They do look like they were used in the Pacific.
Supposedly on Tinian. From http://ww2f.com/threads/inquiry-us-marine-corps-armour-in-the-pacific-war.19411/
These are the possibly earlier pattern that John is referring to. They ‘are’ 55 gallon drums!
Model image only as I’m out of time to find the real thing! From http://www.tankworkshop.com/newshop/index.php?main_page=product_info&products_id=40