I need to find a new or fully functional used TEAC FD-55A 5.25" Floppy
drive for my vintage computer AND new floppy disks (MD1-D and MD2D)
for the same type of drives. The TEAC FD-55A drive is about 6x1.5"
looking from the front and it is built into the computer - not the
external type. The computer is an Apple II compatible (portable
version) built by Taiwan maufacturers in the early 80's. It has 2
drives, but the second drive is giving frequent I/O error and Bad
sector errors on floppies that works fine on the first (boot) drive.
If you need a picture, I can provide one, but I really need these 2
items to get the computer fully functional again.

I'm afraid you're going to have a pretty hard hunt. Have a look at the
link below - it's offering a few 5.25 drives, of unspecified brand.

http://www.n2.net/clairemont/A2/a2fs.html#hard

What is the machines type ? And will it except normal Apple II drives
? Because Apple II drives aren't hard to come by.
Let me know, in the meanwhile I will look in my pile of 5,25" drives
if there is a FD-55A drive there.

There are probably a fair number of compatible plug-replacement drives
for the Teac you have.  A compatible drive may not look or sound
exactly the same, but it will fit in the same space and work the same.

Meanwhile, it sounds like the drive just needs to be aligned which
isn't that hard a procedure.

Disks should be easy to come by.

You should check out some general vintage computing sites on the web,
such as the message board at www.vintage-computer.com, to locate some
expertise on the issue.

Best of luck!

   VC