I lost one of my cards and the company who makes them sent me a replacement card. My deck is over 25yrs old and the new one doesn't match. How can I 'age' the card so it matches?

Honestly there is no way, even if you weather it, warm it, lay it in the sun and all of those things. It would never age the same and would always appear different.

Tarot card? Buy a complete vintage set on ebay.