Guy's he's got a XCR, I'm guessing the one w/ the skeleton stock, which means no chance of fitting a battery to the rear unless he swaps over to a buffer tube stock or fashions up a pouch of some sort for the battery.
Best bet is a FAKE PEQ battery box. Just google "PEQ battery box" and you'll get a ton of hits. Just get one that fits your battery, most battery either specify if they can fit a PEQ box or have measurements so you can figure out if it fits or not yourself. Its literally just a pretty looking enclosure to house your battery, so as long as it fits your battery and looks good to you, its fine. As for recommendations, someone who actually runs a front wired gun w/ a PEQ batt box can chime in there.
Oh and generally no to lasers, you run the risk of damaging someone's eyesight, especially w/ the unregulated China stuff. They're also pretty pointless considering the range and accuracy of airsoft in general. The PEQ batt boxes w/ the laser/light probably also takes up more battery space so just get a plain peq box and you're good to go.
Ignore the Magpul stuff, I think Ricochet was under the impression you had a M4 w/ a RIS/delta ring system. It won't fit your XCR seeing as its a completely different gun.
Just your friendly neighborhood narcissist gearwhore.