I've successfully thinned Tamiya with water, 70 percent alcohol, windex, and Future. But none of them worked well with Tamiya metallics, gold leaf, etc.
I buy lacquer thinner where ever its cheapest as I tend to use it a lot for painting, cleanup, airbrush cleaning, and so on. Home depot, Lowes, Walmart...it all seems to work the same.
Like I said, just be sure to practice first. Once you figure it out (not hard) you'll be amazed how nice the metallics and thicker paints are. No more chunks, clotting, etc.
Hope this helps. And you can also use it on the rest of the Tamiya line with great results.