A mud user lists out all of the parts you'll need to buy from tnutz.com, and fantastic solution for very cheap to achieve a modular roof rack that would typically cost $1000 or more.
Adventure Chaser 100 series build
A little more expensive than the DIY option above, but a bit more versatile.
Landcruiser 100 Series Roof Rack: Toyota LandCruiser 100 Series Roof Rack
97-07 Toyota Landcruiser/ Lexus LX470 100 Series Prospeed Roof Rack
Land Cruiser Roof Rack | 100 Series - Lexus LX 470 (98-07) - Victory 4x4
100 Series Roof Rack - Gamiviti
LAND CRUISER Off-road Armor & Accessories