Something like this, but the cap would be the same colour as the tunic, with brown leather, or tunic colour peak and brown leather straps.
Strathcona's Horse (Canada)
... and from the film 'The War Horse'...
That will do you pretty much until 1938-1940. I have no idea why the guy on the left in the last photo has a different tunic colour... but he has a different cap badge and I'm guessing he's a colonial type.