I lost my W-2 and need a copy to file my taxes. I filed for an extension already. My employer changed hands so I can't get it from them.

If you cannot obtain the W-2 from your employer, then for a fee you can get a complete copy of a W-2 from the Social Security Administration - https://faq.ssa.gov/en-us/Topic/article/KA-02501

You can get a free Wage and Income transcript from the IRS - https://www.irs.gov/individuals/get-transcript

The Wage and Income Transcript from the IRS will not include the state and local information on your W-2 (boxes 15 through 20). If you have to file a state tax return you will have to get the complete copy of your W-2 from the Social Security Administration.