Canon doesn't make a battery grip for the EOS R100. They typically only have grips for part of their full-frame line of cameras.
And, while there may be third-party battery grips, I would advise against using them. Could lead to all kinds of compatibility or other issues.
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Ricky
Camera: EOS R5 II, RF 50mm f/1.2L, RF 135mm f/1.8L
Lighting: Profoto Lights & Modifiers
