I've been using a Rocketfish MHL adapter for the appradio in the wifey's car until I can get an adequate mirrorcast dongle.
I haven't had any issues with it. It also comes with a 11 pin adapter for newer Samsung devices.
The Samsung branded 5 pin MHL adapters should also work and be found in stores(they had them at my local Bestbuy along with the Rocketfish I bought).
I'm not sure exactly what you're looking to do, but maybe some sort of cast dongle might be a better option.
For streaming I like using chromecast best(there's 3rd party ones that support chromecast/mirrorcast/DLNA/airplay in one unit). The user experience is much nicer with chromecast but you're limited to using apps with cast icons and a wireless network(mirrorcast/dnla don't require this).
For screen mirroring a straight HDMI cable works best but not even Motorola puts HDMI ports on their devices anymore. MHL adapters work for the most part just as well but can have more failure points and compatibility issues. I haven't tried mirrorlink yet(I do have a new appradio that supports mirrorlink as well as HDMI but it's still in the box) but from what I under stand it's not as fast as HDMI and may give noticeable lag.
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