How to attach vinyl bracket to cement post?
You can try a self-tapping concrete screw, as long as the concrete is not brittle.  You need to pre-drill a pilot hole but after that nothing more than screwing the screw in.  The only problem is the screw size is probably a little bigger than you need.  I think 3/16 x 1-1/4" is the smallest made, but other manufacturers might make smaller.



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