bought an internal ssd + sata to USB for 80$ with one day shipping. hope this works out, but would still like a easier way to move my 20 rigs over to windows.
You have 2 options (probably more, but these 2 will be your best bet)
1. If you can acquire a windows 10 Enterprise or Education edition, it comes with a built in utility called "Windows to Go" which will create a portable windows environment on a USB drive. I'm sure you can find a torrent with one of these versions. Here are the instructions for installing it: http://www.tomsitpro.com/articles/windows-to-go-in-windows-10,2-1089.html
2. Use the Win To USB utility that others have mentioned here. This will also do exactly what you are trying to accomplish: https://www.easyuefi.com/wintousb/index.html
When researching this, don't get confused with the utlilities that will put the windows cd onto a usb drive and make it bootable. There are a few popular ones out there, but they are designed to allow you to install windows when you don't have a cd-rom.