It would be simple to make it. Just instead of KCl you have to use CsCl in your internal solution. All other components will be same. And the other fact is it is not available commercially as Michelino said.
I wasn't aware any intracellular solutions are available commercially, as what goes into them depends on what you want to measure. If you are making a CsCl-based intracellular solution by substituting KCl for CsCl in an existing recipe, be sure to adjust the pH with CsOH.
We also make our own, and typically adjust the extracellular and intracellular solutions for whatever conditions we need, for example, setting the chloride reversal potential to zero.
There aren't a ready-to-use intracellular solutions, but it is easy to made, and the literature are plenty of recipes of CsCl-based intracellular solutions for DRGs. As you can see everybody makes their own. What current do you want to record? sodium? calcium?
We also commonly use CsF-based intracellular solution to record Na+ currents. It blocks K channels and greatly helps the stability of the giga-seal therefore making patching a little easier. You still need to adjust the pH with CsOH.