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Might I suggest The US Army in World War II (1): THE PACIFIC by Osprey Publishing?
There is also Survey of U.S. Army Uniforms, Weapons and Accoutrements,http://www.usww2uniforms.com/index.html, U.S. Army Uniforms of World War II by Shelby L. Stanton (Stackpole Books, 1994), and many other published books and websites that cover this topic in varying degrees of detail.
The disclaimer on the following site is worth keeping in mind: https://olive-drab.com/od_soldiers_clothing_combat_ww2.php
"Keep in mind that as new items of clothing and equipment were developed, they only slowly made their way into general use. A year or more could separate the first use of an item by one unit and the receipt of the same item by another unit. Some units were still using pre-war equipment in 1945 while other units had the latest issue."
You might also want to visit or contact a relevant Army museum, the National Museum of the Pacific War, or the National WWII Museum.
It is worth mentioning that the Southwest Pacific Area also included US Marines, Australians, and other non-US Army forces, although my reply has focused on the Army part.
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Dear Mr. Schneider,
Thank you for posting your request on History Hub!
We searched the “Encyclopedia of US Army Insignia and Uniforms” by William K. Emerson and located information on tropical worsted uniforms. In 1929, the army returned to khaki after a persistent search for cool, lightweight clothing. Additionally, military units serving at tropical stations, most notably the Philippines, wore locally made khaki uniforms that varied slightly from official cut (p. 509; 488).
We hope this is helpful.