Wcialrlter,
There are many suppliers, the ones I listed may sell the same type as what you have.
Standard Steel Specialty sells direct see attached link for there Website etc.
Standard Steel Specialty - Servicing the Power Transmission, Automotive and Aerospace industries since 1925
8020 sells tons of aluminum extrusions, see attached link for info:
https://www.8020.net/
Welcome to the Zone,
Jeff...