Not really sure how a "baritone ukulele" specific tuner will be useful or different in any way to any clip-on tuner available..
In fact, the idea itself is redundant.
If you have a tuner set to tune "Guitar" - it will read the Baritone ukulele's strings as 4th (D), 3rd (G), 2nd (B) and 1st (E).
So a guitar tuner is already a baritone ukulele tuner...
If tuners had a conscience, as far as it is concerned, a baritone ukulele is just a guitar lacking a 5th and 6th string.
That being said, I always just use my tuners as Chromatic. I prefer to read my strings as individual notes than as numbers