  We present a successful synthesis method of the series
Ga$_{x}$Cu$_{4-x}$(OD)$_{6}$Cl$_{2}$ with substitutions up to $x=0.8$. The
compound remains a frustrated kagome system with an insulating ground state
similar to herbertsmithite for these substitutions, as the additional charge of
Ga$^{3+}$ is most likely bound to additional OH$^{-}$ and Cl$^{-}$. Besides
infrared measurements, we present magnetic and specific-heat data down to 2 K
for selected samples with $0\leq x\leq0.8$. With increasing $x$ the long-range
magnetic order is suppressed, similar to what was observed in the series
Zn$_{x}$Cu$_{4-x}$(OH)$_{6}$Cl$_{2}$, indicating that Ga goes predominantly to
the inter-plane position of the layered crystal structure. The reduction of the
frozen magnetic fraction with increasing substitution was followed by $\mu$SR
measurements. $^{69,71}$Ga nuclear magnetic resonance (NMR) was applied as a
local probe for Ga induced disorder. One well resolved Ga NMR line of moderate
width is found for each isotope across the phase diagram which indicates a
rather homogeneous distribution of the Ga isotopes on a single site in the
lattice.
