Because sometimes we DON'T have a choice. You could fix that by upping your side-hustle lock business.
Make both of the locks you currently produce to fit the left side of the gun.
Introduce a Durs Egg or Manton lock and make them for both sides of the gun. People still scratch-build pistols and double guns you know and those that do don't like having to use locks that suck, especially if they're building them to sell. You won't even have to offer gun kits for the new lock styles, just sell them outright and offer spare parts. Seems like it would be a big return for relatively small headache compared to introducing a whole new kit.