I'm on my first colony and I was importing alum through the uranium enrichment center but the update made that cost more money than I could possibly make. I just built a galactic trade building but the aluminum is even more expensive there. I have 849 al left and I'm not sure what to do to get more aluminum since I can't build an archeological dig site and I can't import it.
You'll have to build aluminum bots and go mine aluminum from the deposits around. If those are gone consider asking your commonwealth leader.