The new bathtub drain basket won't fit the opening on my 50 year old tub. The opening is too small. What should I do? Do they make drain baskets with a smaller diameter?

The new bathtub drain basket won't fit the opening on my 50 year old tub. The opening is too small. What should I do? Do they make drain baskets with a smaller diameter?
Your question's confusing. By "drain basket" are you talking about the tub shoe or the tub waste and overflow? (See image) Let me know, Tom

Yes they do make them in different sizes. Measure the opening in the bottom of the tub and them measure the new shoe before purchasing.

I guess it is the shoe I am talking about. The silver part in the picture above. It is just a hair too big to thread in.

Where do I find the slightly smaller size? Or, where do I go to order one as my local home improvement stores only carry the one size? Thank you.

Most tubs have a access hold located directly behind the drain. Why not simply replace the old tub shoe? I'm curious. Why did the silver drain lip get removed in the first place? Regards, Tom