On the download and download and install macOS (for making a bootable installer) MacOS Mavericks is strangely missing from the list? What's the reason its not listed and is there another Apple source or similar to get it from?
(I did not know what the best tag would be for this because it's more of a "Apple support page/website" problem, however it ties into MacOS)
Earlier Mac models
Can't say why it not on How to download and install macOS - Apple Support
You may be able to find it by doing a web search for OS X Mavericks. I wouldn't vouch for anything you might find.
I would think either macOS 10.8 Mountain Lion or macOS 10.10 Yosemite should be equally fine if you want Mavericks because of software compatibility issues. Otherwise, I would go with at least macOS 10.11 El Capitan or an even later OS if your Mac is able to run a later OS.
No option to download MacOS Mavericks 10.9
