Is there a way to get a copy of an old closing statement? Is there a formula (% of buying price?) I can use?
No, there is no formula to determine all of your closing costs that would apply in all situations. Title search costs and title insurance is based on the amount of the house in some states, but not every state is uniform.
You can try contacting your realtor or you can go to the county records office to see what they have recorded.
Typically, either the lender or the closing agent will maintain records for 7 years. So you might try contacting the lender and/or closing agent for a copy. You can expect to pay a small fee for this too.
I was in the exact same boat and then I searched my email from the timeframe I had been communicating with the title company and my agent. I discovered that the closing agent had provided me an advanced copy ahead of our closing appointment. Might be a longshot but worthy of the effort to search.