I have a defective music device. It's a MOTU MIDI Timepiece AV USB midi
interface. The problem is that the USB is not working. I'm hoping to
fix the unit myself, because sending it to MOTU for repair would cost
a good chunk of the value of the unit.

A few of the IC's on the main board are seated in sockets, so I decided
to try a simple swapping method to see if any of the IC's could be the
problem. I got a working unit of the same kind and swapped IC's until I
found a particular IC that seems to be the source of the problem.
(Whichever unit has this IC fails, regardless of what other IC's are in
it.)

MOTU doesn't sell replacement parts, so if I want to replace this IC
I need to get it from a third party supplier. Now, I don't know a thing
about IC's, so I'm lost here. The IC is marked:
CG5273DM 64013PC
IND9940
516070

Google comes up with lots of hits on the first code, CG5273DM and no
useful hits on the others, so I'm assuming that first code is what's
significant.

Now, a bunch of electronic component suppliers carry IC's that have
that designation of CG5273DM. They all have the right number of pins,
but vary in terms of the dimensions of the chip (which is listed in
some cases). The chips are described in some places as a DIP-28L
audio echo processor. That doesn't sound to me like it'd be used in a
MIDI interface, but what do I know?

So I have a couple of questions:
1. Is there any chance in hell that if I buy one of these chips from
a third party it's actually going to be the right one and make my
unit work?
2. Where would I find a supplier that would sell me a single one of
these IC's? Buying $100 worth of them (or whatever the minimum order
of the wholesalers is) would not be much better than sending the unit
to MOTU.