Lens for Vintage Glasses

I am looking for recommendations on reasonable priced prescription lens for my current frames.  I love them.  I don't want new frames, and I realize that they may be damaged (every optometrist location has told me) when they try to fit new lens in older frames.  All the boutique places seem extremely expensive and places like costco feels like they won't even try to be careful.  I can't be the only person who doesn't get new frames every time their prescription changes.  Please help! Thanks in advance...