Is there any company that makes an INTERNAL USB interfaced floppy drive?

probably not, because it wouldn't be worth it to develop the technology. why don't you just modify an USB HD enclosure, they are getting pretty cheap these days.

I think the product below is what you are looking for!

Ultra ULT31793 -- 7-in-1 internal USB cardreader with 1.44Mb Floppydiskdrive costst approx. $20- $30.

I'm not sure if it works in OS X, but I don't see any reason why it shouldn't since most USB Floppy drives work using the default USB Mass Storage system.

This is how it's looking:
Click to view attachmentClick to view attachment

Besides the Floppy functionallity it also supports:
- Secure Digital (SD)
- Compact Flash (CF)
- Memory Stick (MS)
- MultiMediaCard (MMC)
- Smart Media (SM)
- MicroDrive (MD)

If you buy this device please post you experience, I'm considering to buy one too.

While browsing this Forum i saw another topic which is dedicated to these type of devices..

Probably interesting to read the topic:
http://forum.insanelymac.com/index.php?showtopic=43205