Usually the (aftermarket) Headlight brackets, that bolt to each fork has an extra hole, that the indicators thread fits through.
Otherwise you will have to get creative. Search "motorcycle indicator brackets". These often are a small straight bracket with 2 holes in. The smaller hole will secure to an existing bolt somewhere (each side), with a larger hole at the other end, for the indicators thread to fit into. Another option, fork mounted brackets. These are all universal fit, so plenty of options out there.