As you can't change the lens on that camera then what you need is a teleconverter. Sony would probably have one that's 1.7x to 2.0x that'll work as well as any. Given a choice of converters go for the HD one and the best one Sony make.
Depending on what and where you're planning to shoot through the teleconverter the results you get can be disappointing from my experience and that was on a SD camera. HD and the compression used on consummer cameras could make matters worse for you if there's heat haze.
The HDR-SR12 has the Active Interface Shoe.
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A better microphone...
depends on what you are recording. A day at the zoo with family I would not
bother being a video geek and adding all the gadgets while family waits
for you. The mentioned mic might not be all that bad.
Recording voice from across the room for a child's school report I would
use a stereo mic that has a 1/8" plug and a stereo extension cable to
get the mic closer to subject and away from the camcorder sounds.
(motor whine and you fumbling with zoom etc.)
Okay, based on your helpful link I ordered the Sony ECM-HGZ1 Shotgun Microphone.
Now another question. I ordered both the mike and a Sony HVL-HIRL IR NightShot and Video Light, but there is only one shoe. I can imagine wanting to use both at the same time. Is there a way to have an outboarded shoe-equivalent?
If they use the "hot" shot part of the interface probably not.
If you don't need that, just a vanilla cold shoe then Rycote make a hot shoe extension which isn't "hot at all. There's quite a range of brackets that might get you what you need.
Probably a good idea not to hang everything off the top of the camera anyway.