Meaning Tundra arms/kings might be better overall than stock LC? If so, it depends on your goals. This may be worse for cornering (sway), but better in terms of total travel/damping/soaking up big bumps in the desert/crawling/etc. But it would probably be worse than stock LC for corner lean.. they are particularly good with that. You should see how thick a KDSS sway bar is.. it's crazy. But that plus the off-road capability is only possible due to the disconnecting nature of the KDSS system.
The issue is where to get the stiffer bar. Someone suggested a diesel 200 might have one available.. I assume due to the extra weight of that engine package. You'd have to do the research to see how much different it is, if at all. But, if that diesel 200 doesn't have KDSS it will probably bolt up with the correct brackets/bushings/links, as toyota tends to make things like this mostly interchangeable.
I don't know the measurements, but a 2013 US LX570 URJ201L had front sway bar part number 48811-60280, while a 2013 Australian Landcruiser VDJ201L without KDSS had a slightly different 48811-60290 (-90 vs -80).. so the number is different. Finding measurements could be tough. Probably need to locate someone with one of these and have them measure the diameter with calipers to compare to yours. The bushings have different part numbers while the bushing brackets are the same, which implies the inner diameter of the bushing is different.
IF it is thicker, and you can get ahold of one here in the states, I think it would bolt up. But this could be a lot of cost for very little gain.. it is probably much cheaper and easier to throw a set of globes on yours and see whether it changes things favorably.