This is a drain cover I made to give me that extra couple inches of water. 

CAUTION: Do not leave the bath unattended while filling. You could cause flooding and serious water damage to your house. The overflow drain is there for an important purpose, be very careful.

This cover will work if your drain looks similar to the pictures and has a diameter (to the outside of the threads) of 60mm and the threads are spaced 3mm apart. I have included the Fusion 360 file so you can modify it if it doesn't work for your drain.

There is a blank version and an embossed version. Print face down with no supports. 

Enjoy a luxurious bath!