Help me find aluminum for my trailer

[SuperDutyScaler]

Ok ive read threads about making a tamiye flatbed trailer to amore scale 48ft, and most of yous found it at local home depot or lowes. Well i dontknow if its cuz i live in crappynew jersey orwhat but i checked three home depots, two lowes, a ace hard ware, a true value hard ware, and one mom and pop hard ware and cant find anything close to tamiya frame stuff! Can someone post a link or something so i can finish my trailer and king hauler please?