Help with British Colonial Uniforms

Does anyone knows anything about the original uniforms of any of the following units? Any help with Any unit here will be good.

Chinese Gun Lascars (Any uniform of this unit will be usefull)
Falkland Islands Police Force
Gambia Police Force (Any uniform of this unit will be usefull)
Gold Caost Rifle Corps
Oil Rivers Constabulary

So, after some research, I found some information about some of those units, but the others here are the ones I couldn't find anything. Any idea guys?

Dear Abadu,
Can you share your research?
I have an image related to the uniforms of Gold Coast Constabulary and Hong Kong Engineers
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Ceylon Mounted Rifles
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Regards
Shams