Looking for Smallest Capacity and Lowest Cost 2.5" SATA SSD (or Maybe HDD)

I have a test computer that has a clean OS installation - nothing installed except Windows updates. I want to take a system image of the OS and be able to reinstall the image whenever I need a clean system again. This is for testing of software and software installations.

A clean OS will easily fit on a 64GB drive (actually, 20GB would probably be enough). So, I'm looking for a small capacity internal SATA SSD (or maybe HDD) that I can fit into the PC to store the system image on.

I recall that 64Gb SSD's used to be available, but I can't seem to find any except on eBay, and I'm not sure about the sellers there.

Can anyone please point me to any bargains?