I had the EXACT problem last year . Someone had ran the clamp on the tube loose(previous owner of wide front I bought) and thats what happens!.
Just take a fine grinding disc and clean the area up,weld around the elongated sides of the hole,and then take a die grinder with a burr and SLOWLY work the welds until a new pin of the correct diameter just slides back through he hole.
Also,if you wanna "cheat" a little,you can find an aluminum/brass/carbon rod the same diameter as the pin and just stick it through the hole and wels around it. The weld will avoid those materials and help you make a "clean hole,but I like the FIRST way I did it the best. ;)