Wrought Iron Stair Rail Anchor Replacement?

I have extremely loose wrought iron railings (approx 25 years old) on exterior stairs. Tightening doesn't help. I've managed to remove all of the old anchors and am now left with 1/2" holes that are too large in diameter for the replacement anchors I intended to use (Parawedge 3/8" by 2 3/4"). The 3/8" anchors will require me to enlarge the holes in the railing mounts and there is not enough room on the mounts to enlarge them to accommodate 1/2" bolts. Is there a reliable concrete patch that I can use to fill the old holes and is strong enough to securely hold the new 3/8" anchor bolts? I guess I need some type of super epoxy or concrete patch to fill the old holes and then re-drill for the new ones. The railings cannot be modified in length, so I need to use the same mounting spots. Any help appreciated.
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Rawlplug makes a 2-component epoxy that ends up stronger than the concrete surrounding it. It comes with the corresponding fasteners. (The larger OD stuff is used on highway signs, etc.). Finding it retail could be the hardest part.
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