Convert String to Sprite

Hi, I need to convert a string to a sprite.

I tried making an array of 99 sprites, but it causes the scene load time to be slow (this scene is loaded often)

I decided to instead, have an array of 99 strings, pull a string from the array and convert it to sprite.. But can't seem to find anywhere how to do this:

Pseudocode:

String imagename = "Thetestimage";

...

gameObject.Sprite = imagename;

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instead of (which is the way I think most people will suggest doing this)

public Sprite spritename ;

...

gameObject.Sprite = spritename;

Thanks for you time.