This is a problem that the refrigeration retrofit industry has had for quite some time. One of my customers approached me about this issue and we designed a proper solution.
There is often a problem during maintenance while installing trying to install a new motor to an oddball coil on an existing evaporator. Up until now, there was only one option (Buy a new complete fan/motor unit).
The 977-series fan guard comes in Black Powder Coat or Zinc Plated finish.