Diasclaimer:
This modification procedure may be succeed if working very carefully.
If not, you are the responsible person.

Thechnics FDD differs from the IBM standard!

1. Put the keyboard upside down on a soft surface.

2. Read the service manual to locate the fixing screws. If any stays unopened, you propably break the plastic support when trying to detach the cover halves.
http://www.dlc.fi/~matsai/Keyboard/KN5000/

3. Unscrew only needed parts, I haven't documenetd them. Don't use force.

4. Remove the old FDD

5. Read the Excel instruction how to modify the FDD cable.

Main procedure from the Excel:
Connector pins have a locking clip. Gently press the clip with e.g. tiny screwdriver or pin and gently draw  the cable to loosen the connector. Do followin changes:
1) from position 4 to position 34
2) from position 6 to position 4

6. Modify the Gotek FDD USB by installing an normally closed push button switch (impulse) to Jumper position J5. This performs the 'insert disk' function.

7. Test the system to work properly before final assembly.

9. Use physically small USB memories, and not larger than 2MB. There are FLASH drive sizes hardly larger than the USB connector itself and same size USB microSD adapters.

10. Best formatting software and instructions from Ketron pages:
http://www.ketron.it/index.php?option=com_content&view=article&id=452%3A-floppy-usb&catid=2%3Anews-2009-2010&Itemid=114&lang=eng
http://www.ketron.it/index.php/?option=com_content&view=article&id=449&Itemid=20#software

You can buy the FDD USB drive from Ketron, but that is available from cheaper sources, I ordered it from Gotek India, Kwality Enterprices.
http://www.floppytousb.net/

If you mention that you are not sure if it works, they may give you 50% discount for the first piece of order.
The actual manufacturer is possibly in China.