The Japanese models are not 22.5" scale, they are 24" like a standard Mustang. If scale length is your concern, then a standard 24" scale Mustang will feel very similar to a Les Paul, so you don’t even need a Mustang. You can choose either one and get a similar range of fretboard stretch.
If you want a smaller scale length, and a smaller body, then you want a Musicmaster, Duo-Sonic, or “student scale” Mustang from the '60s. You can identify them because the last fret on the board will have the dot inlay. If the last fret does not have a dot, then it’s 24", not 22.5".
You can find them used for between $700 and $2000 on Reverb.