Health food store or amazon.
I tried using chick starter for my last batch of turkeys, because I couldn't get turkey starter. I top dressed with brewers yeast for the first 3 weeks, wasn't long enough. Had a high mortality rate and a very slow growth rate. I'll never try that again.
I've attached the Turkey recipes that the Sustainable Poultry Network uses for Heritage Turkeys. Compare the guaranteed analysis of the second recipe to your chick starter. Go armed with data and your own analysis.
You may find this interesting... I use Tucker cause that's what I can get. I reached out to them about their chick starter and they confirmed it wasn't suitable for Turkeys.
Here's the file.