Re: Mbira tines
Cool. Never seen one of those before. I have a 25 key Mbira that I had to completely take apart and rebuild in order to tune correctly. There are lots of good schematics for tuning online. In terms of finding the material, go to a metal shop, or find a welder, or metalworker and ask them where they get their supplies. There are probably more shops than you realize really close to you. You can buy large pieces of spring steel, but cutting, shaping and finishing it will be another huge part of the project. You may already have the tools though.
I can definitely see why the instrument in the clip was so expensive. It was not only tuned perfectly, but there were some really intricate engineering done to the keys themselves. Definitely a pro job. Good luck. Post more if you decide to undertake this. Mbira is a really beautiful instrument.
I re-read your original question. High carbon spring steel is not the ONLY metal you can use. You could always use cheaper metal i.e. aluminum. Or find scrap steel in a junk yard. Might be cheaper to buy a couple of car hoods to cut up and experiment with first.