[ʦ], as in tsar, rats lacks a corresponding IPA diagraph.
The voiced counterpart of [ʦ] is of course [ʣ]! These are IPA symbols
for them. Even UniPad has both, though for practical reasons it doesn't
provide ready-made symbols for all possible affricates: to transcribe
retroflex [tʂ, dʐ], or lateral [tɬ, dɮ], you have to combine two characters.
In most English realisations, [ts] is not close-knit enough to be a genuine
affricate (like German z or Polish c);
it's phonetically a stop + fricative cluster. However, in many British
accents (such as Cockney) fortis /t/ is affricated rather than aspirated,
and becomes a genuine (apical, alveolar) [ʦ], e.g. time
['ʦɒɪm].