Hi Marius,
Chat to Ian Rubie as he can supply Toyota OEM much more cheaply (he works alongside Greg, so can advise on what's available). Whatever you do, don't pay the crazy Toyota prices - it's probably cheaper to book a cheap flight to Dubai to buy OEM ones there and bring them back in your luggage!
I replaced mine with Iezura, which (unscientifically) seem to be a bit better than the Milner ones - I say seem better because fewer of them have been broken, even with big tyres. I am sure that in reality there are various batches from various manufacturers floating around - some better than others and the Toy ones undoubtedly the best.
My thinking is I would rather buy 3 cheapos for much less than one Toy OEM one and replace if I have to. But pottering around the UK, a phonecall away from the AA, is hardly a big issue if I blow a CV. In Africa it would be unless you have a spare. Changing one is a couple of hours work, so not a train-smash if you have a spare. Frankly even if you only buy 2 new ones, I would hang on to the old ones for spares.
I don't think an overland trip through Africa is likely to result in a blown CV - the cowboy stuff at Lincomb puts much more strain on them
Cheers,