Yes it's home made.
The tops can be bought from most places who do work on off road motors. I got mine from a local independant L/R garage.
Total cost for the snorkel, including the top, is about £35. All steel, and nothing sticking out from the wing to catch on trees etc. I have seen quite expensive ones crack or split after catching a tree.
Only takes a couple of hours from taking the wing off to replaceing it.
You can get the forward/rearward faceing tops if you prefer that look.
Pete.