If ya don't find anyone, try
Weldcraft Wheels Wheel Widening Wheel Repairs Wheel Restoration. If you look under "widen" the picture displayed is my rim they did for me when I was building my 70 Camaro. Took a 18x8 and made it into a 18x15, the guys do great work... And it was balanced to 1/4oz when I had the 31x18.5 tire mounted on it.