How to enter special characters on the UOM form - such as the little 3 for cubic, as in cubic centim

 We have a need to define additional UOM in Purchasing for metric measurements, such as cubic centimeter, square kilometer, etc.  I found how to enter special characters but they take up 2+ bytes each, so i can't enter cm³ in the 3 byte long UOM field .    How do others handle this without using DFFs and customizations?

I read note 953344.1, does it mean customization is the only solution?

Thanks,

Jo