As Johnny J mentioned, the baritone ukulele commonly uses the D-G-B-E tuning, identical in pitch to the top four strings of the standard guitar tuning. Baritone ukulele chord charts can be downloaded from a number of popular ukulele sites, and you can use bari uke tabs as well as guitar tabs; the bari tabs will already reflect any necessary or desired adaptations for 4-string playing.

If possible, find charts which identify which string plays the chord root, since this is a key to finding chord alternatives and inversions up the neck. Lacking that, figure out and mark the roots yourself. In the back of Ukulele Fretboard Roadmaps, by Fred Sokolow and Jim Beloff, you can find an excellent root-identifying chord dictionary which (thankfully!) is expressed as generic movable chord shapes and hence is as applicable to bari uke and Ren guitar as to both serial and reentrant standard ukes. The rest of the book is specific to reentrant ukes in C tuning, so probably not greatly helpful.

Sadly, due to reentrant tuning myopia, the UFR chord dictionary lacks some of the wider chord shapes which come in very handy with serial tunings, such as the 1343 major shape (uninverted, rooted on the 4th string), the corresponding 1342 minor shape and the 5431 dominant 7th (uninverted with no interval gaps, rooted on the 4th string). I don't know how the neck length of the Ren guitar compares to the standard guitar or bari uke, so I don't know how feasible these wider chord shapes are for that instrument, but I use them quite a bit on my serially-tuned ukes.

If you look at "fixed" chord shapes (those with open strings) in a normal bari uke chord chart and imagine fretting the open strings just before the nut, you should be able to find most of undocumented but useful "wider" movable chord shapes. Guitar charts are less useful as a source of chord shapes because they fail to consider either the need for the top strings to sound the chord as completely as possible or the ease of fretting only four strings with closer frets.