Unfortunately, the Epson SMD-series are really kind of pieces of junk. I have 2 bad SMD-380s sitting right here, and I have had one other.
The only way to get a new one (I think) is from Best Electronics, for $75 (or more?) plus shipping. Unfortunately, when you purchase a used one, it's likely to be a short-lived piece of junk, too. After all, if it were in a nice (nice = unused or used very little) machine to begin with, they probably wouldn't have been parting that machine in the first place. Trust me, you won't want to trust a "good used" one.
There are places selling replacement drives (square bezel) on Ebay. Most seem to be in the U.K.
These places will not respond to questions about their mods to the drive. I suppose they regard it as a trade secret or something. I just wanted to know if it was indeed modified, and if it needs to be, like the Sony 920MPF does for Amiga. I think the Amiga needs similar mods, but there is likely some correlation. I don't know if Amiga does the same non-standard (or so I am told) disk change detection. Perhaps that is another mod? But this thread from the English Amiga board, on the topic of the 920MPF Sony drive may be of some value......
I've been using the HxC SD-card floppy emulator so much, that the burden of maintaining working actual floppies has somewhat diminished. I have a couple replacement drives Ebay drives. (I also have some new 920 MPFs) I slid the sheet metal covers off just to look, and I did not observe any modifications. I was pretty much expecting to see something similar to what's done to the Sony drive in the above Amiga thread. I plugged one in and booted. But it seems I think there was some little quirk I can't remember, but since I was so thrilled with the floppy emulator I lost interest. I'm going to have to dig one up and try again. You have to cut out the case a little bit to get these to work, but it's not a whole lot of cutting. It should, of course, be done neatly!