An odd combination, grass and steel types.
Well, this is when Ferroseed fits the bill exactly.
Maybe Ferrothorn is your end goal?
Here's how to get one and evolve it.
Shiny Ferroseed Guide
Where To Find Shiny Ferroseed
Ferroseed can be found in the wild, snow or sunny/clear weather conditions will boost its spawn rate due to being a steel/grass type.
They can be found in 10km eggs, Research Encounters and Raids too.
How To Evolve Shiny Ferroseed To Shiny Ferrothorn
Evolving Shiny Ferroseed will create Ferrothorn.
It takes 50 Candy.
If you have enough select it and your Pokemon will evolve.