You could get an alloy rack and ladder. Front Runner in South Africa make one for about ZAR 4700 / USD 720 (ex factory). This may be viable, depending on shipping costs. Check out
Front Runner. Click on Vehicle Specific Poducts > Landrover > Defender 110
In my opinion, these racks utilise superior materials and design than the original galvanised one from LR. And they're proven in real African safari and other off-road conditions.
