A while ago I sent a message over to Vortex about the lack of a light weight, fixed power optic on the market at reasonable prices. This specifically with the Lever, and other short range carbines in mind.
Theoretically it would not be that expensive, would be notably lighter and simultaneously more robust than a variable optic, and could come in especially compact, with a wide FOV possible.
They told me it was an interesting concept, but it had not crossed their minds before (I doubt that), and that they had no current plans to do so.
While I am generally a fan of a 'naked' lever gun, a low powered optic to clarify target beyond 100 yds is useful. A set of low see-through mounts keeps the open sights open, and the parallax issue virtually doesn't exist because of the short range. (AKA the ol' Pennsylvania woods gun).
Many levers came to me in that configuration with the seemingly then ubiquitous 4x tasco or bushnell on top.
To answer the question, any light weight low power optic with a wide FOV. If you go too narrow, it defeats the purpose of a short range carbine.
