Where can you purchase a top-lever spring for a Remington model 1893 single barrel shotgun?

You can purchase a top-lever spring for a Remington model 1893 single barrel shotgun from several sources. Check specialized gun parts retailers online, such as Brownells or Numrich Gun Parts Corporation. Additionally, you might find it on auction sites like GunBroker or eBay, or at local gun shops that stock vintage firearm parts. It's also advisable to join online forums or communities dedicated to vintage firearms, where members may have leads on where to find specific parts.