There are no internal PC (PCIe, etc.) floppy controllers being manufactured anymore, and I don't believe there was ever a PCIe one.
Get an external USB floppy drive and either live with it outside your chassis, or hack it apart an mount it internally.
Here's a YouTube video of a guy hacking a 3.5" internal Floppy/Card reader drive and combining it with a USB external floppy drive to create a working internal USB floppy drive: Making an Internal USB Floppy Drive