I have an internal one listed on eBay right now as well. It's brand new (*new old stock) and it's an Amiga XL internal drive for A4000 / A4000T. I did test this (used it to set up an A4000 about 7 months ago then sold the A4000 with a DD drive).
It's actually perfect for an A4000T as the 3.5 drive bezel is regular 1/2 height and not one of those crazy taller drives that shipped with 1/2 the 4000 desktops.
http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&rd=1&item=5137947436&ssPageName=STRK:MESE:ITI think twenty bucks is pretty reasonable for an internal HD floppy drive that is 2x as fast as the original Amiga HD drive. :-)
(Yep I'm (catherder) from eBay, I forgot my old acount name on Amiga.org so I made a new one
