Amazon seems to be having an issue with their appstore on Fire TVs and more. Searching for common apps is not bringing up the listing for the app you want, even though the app is still in the appstore. For the time being, your best bet is to find the app on Amazon’s website and then select to send the app to your device from there. The search on Amazon’s own site isn’t working too well either, so you may have better luck finding the listing through Google. For those of you looking for Downloader, you can find it here and use the drop-down menu on the right side to send it to your device.