Angels have the Phone Box
One of our members has developed a custom recovery media, which you can find here:
Windows 10 Recovery Tools - Bootable Rescue Disk - Windows 10 Forums
It would fit on a 2GB stick.
If you want the W10 operating system (for future installation or DISM procedures) it would fit on an 8Gb stick.
If you're talking about creating bootable recovery media from an OEM using their pre-installed software, it could be slightly larger, but should still fit on an 8GB stick.
Images of your entire hard drive should be kept on an external hard drive.
Hope that helps.