Since the folks at Ziggurat don't care enough to add the expansion manuals to this release, I've scanned my physical copies and you can now find them on Archive.org.

Megafortress: Operation Sledgehammer Manual

https://archive.org/details/megafortress-operation-sledgehammer-manual

Megafortress: Operation Skymaster Manual

https://archive.org/details/megafortress-operation-skymaster-manual

Enjoy!