Tamiya Black Panel Liner

A Google search turned up a fee places to get it

https://www.google.com/search?q=tamiya+black+panel+liner&oq=tamiya+black+panrl&aqs=chrome.1.69i57j0l3.13209j0j7&client=ms-android-verizon&sourceid=chrome-mobile&ie=UTF-8

Or just try making your own 

Very few USA sources have them in stock. You can buy them direct off eBay from Asia. Takes at least a few weeks to receive. Use the seller with the highest rating. You can also buy a tin of Humbrol Black from Megahobby and their enamel thinner and make your own wash. Easy. You can also use oils as Abt 502. Just be sure to put a small smear of oil paint on a piece of cardboard (to remove excess oils) and leave overnight before using. Use mineral spirits to thin. Oils work great.

I've gotten it recently from Squadron. Guess I got lucky.

Jim  

I have run into this a couple times with Tamiya, the first was  popular military colors were OOS for a while.

Recently it's the X20A thinner in the larger bottles that I had been unable to find available on line anywhere for a couple of months now. Walked into my local hobby shop a couple weeks ago and they had 4 large bottles so I bought them all.

My advice when it comes to Tamiya products now is don't buy just one, stock up. Because you never know what might be in short supply next time. Good luck finding your panel liner.