[Sawstink]

Hey guys, this question has probably been asked but I am short on time and haven't been able to research it much

I was deciding on either the G&G M4, or the G&G M16. I like the M4 for it's retractable stock, but it is just too short, so I was wondering if a retractable or folding stock would fit on an M16, or it this wouldn't work because there would be nowhere for the battery to be housed.

Also, if this is possible, would you please post some links/pics of a cheap stock for an M16? thanks in advance guys