The device you need is the Catweasel card. There are several versions, I think the Catweasel 4 Plus is the latest for PCs. You need a PCI slot to install it, and a regular internal PC floppy drive.
I've never used one with WinUAE, but I think the way it works is that WinUAE passes the Catweasel through to the Amiga emulation and AmigaOS accesses it just like it accesses the Amiga version of the Catweasel card - through multidisk.device and a DOSDriver.
So unfortunately (my understanding - hopefully someone will correct me if I'm wrong) the AmigaOS has to be running in UAE. In other words, the Catweasel won't present the attached drive as DF0:, so you can't boot your emulator from a real Amiga floppy or use it for non-OS-friendly games. But if you just need to recover some files and save them to a new location, this should work fine.
If you're not already familar with them, there are a few solutions out there now that can create whole disk ADF images of Amiga floppies. The Catweasel can do it (outside of WinUAE), there's another hardware product called KyroFlux, and there's a program that requires just 2 PC floppy drives.
