Molding / casting

Hi, Back then, I have bought several real boeing type switch knobs. and they each are single type of knobs. But In reality, inside of most boeing cockpits there are some duplicated knobs that are used on each panels. So, back then I was advised in order to make duplicated swicthes I could do molding and casting. And the first attempt I did was using rubber modling, and clear resin casting. but they did not come at good result. I wasn't really pleased how it look. Asking for your help, would anyone know or suggest the best method, or maybe type of molding and casting to get that switch knobs to look almost indentical to real one without any glitch? I have vised some of the builer's website showing how to do molding with plaster, or casting with some type of resin. but most of product they use has to be ordered. I just wanted to have one that can be purchased at hobbies stores. So please do let me knowThanks