I am also looking for something like this, but instead of kids, I have dogs who like to jump into and out of the cabover bed. I would rather that they didn't do this ...
I've looked at those bed rail systems, but the way my cabover bed is constructed, the mattress is integrated with the piece that goes over the cutaway (and then there's a u-shaped mattress that goes around the front and sides), so something with "legs" that tuck under the edge of the mattress wouldn't work.
Camping World sent me a promo last fall on a 90" x 18" cargo net that would have worked perfectly, but when I clicked on the link the item was discontinued. Talk about frustrating! I've looked at the pickup truck nets that replace a tailgate, but none of them are wide enough. Can someone show me how they have actually used one of these tailgate nets to cover the cabover bed opening?