Goto
http://www.caseoutlet.com
Look under the ACCESSORIES and find the slim floppy with adapter.
Price is $25.
This is the exact same one I used for my 4100.
In the bottom picture you see the small ribbon cable fom the slim FDD, then the adapter that you plug a regular floppy disk cable into. On the back of the adapter their are exposed circuits. I took a piece of plastic from the case of one those AOL disks I am constantly getting in the mail, and made a back for the adapter, a couple of holes to match those on the adapter, (2) all-plastic push tabs, and wham I had a adapter that would just lay in the case next to the FDD socket, without shorting anything out.
If you get a MaxAttach 4100 with a gigabit adapter then it will be in the slot where your floppy will go. In the back of the case! It's the about a 1/2" x 4" slot on the back of the computer. The slim floppy will fit here with a bit of coaxing, it rests on the empty PCI slots. Version 2 HDD of NASLite coming out soon will eliminate the need for a floppy, and boot from a HDD. I'll be glad when it becomes available.
Hope this helps,
JSykes