But, I used to want something like this when my kiddo was tiny. You know the stage where you are changing their diaper every half hour or more. I got tired of pulling off pants, but with the diaper covers I make without side openings, because I am a lazy no good sewer, you had to completely pull them off. So during the winter, I put my thin little socks on her so that she wore them like thigh highs, so I could change her diaper, not take off pants and keep her legs warm.
So, that snow suit I made out of two wool sweaters left me with some skinny sleeves. I am sure any shrunken wool sweater sleeves that don't have enough material to become Diaper Cover Longies will make fine leg warmers.
My model was getting a little weary of modeling. Please ignore stressed out facial features; they were not caused by the leg warmers.