Recreating The Blank/Empty Spawn Egg Help.

(Sorry if the tag(s) are wrong, I’m not sure what the tags are to fit what I want)
I’m having a hard time figuring out how to change the texture of a spawn egg. I’m trying to recreate the blank spawn egg that disappears on 1.12.2. I don’t know why I love this item. It just seems cool to me. I’m currently working on a command that I can use to make the egg seem “useful” so it reacts when touching the ground (still a work in progress). I’ll have to eventually figure out how to keep the egg after I spawn a slime in the world, but right now, I’m trying to figure out how to change the texture of the spawn egg.