There's a video on the Aquaticlife web page showing how to replace the LEDs on your type of fixture.
http://www.aquaticlife.com/products/286#
Pops out quite easily and it appears you simply discard the whole plastic LED assembly & plug in a new one. Can probably get a replacement from them. But before doing that, why not remove the broken LED assembly & see if it's possible to unsolder the dead one and replace it with an equivalent 1 watt replacement? They're quite inexpensive these days. I imagine the Aquaticlife assembly will cost a few dollars more than just a discrete LED & might take some time to get.
If there was more info on the power supply in the fixture that runs the LEDs, you might even be able to upgrade to a 2 or 3 watt LED. Just need to make sure that the LED driver in the fixture can handle the higher power LED. Might also need some added cooling though. Same goes for adding strip light you linked to in your post. You need to verify the power output & voltage of the LED driver in your fixture to see if it will work. Looks like the one you're looking at has it's own small power supply, probably 12 volt DC. Since you only have two LEDs in your fixture now, the driver is probably more like 3 or 6 volts.