I've had the same dilemma. Not many roof light bar mounting options for our truck without drilling.
I've tried a UK CF member(also Navara forum) but haven't received a response as well - the link below will give visual of what I'm shooting for.
The latest project - LED front light bar
There is a
thread of a group (Offroad Gorilla) working on a prototype LED mount using the roof rack bolts. The guy has done it with his Xterra and sells them - I've been in contact with him over a year and half and no luck to date for the Frontier.
I recently found a local fabricator and Waterjet cutting service shop that may be able to fabricate mounts for my 40" light bar using the outside bolts on the roof rack(they recommended aluminum of course).
I'm meeting this Friday - if it gets any traction, I'll share the info with our group.