In reply to Pyreneenemec:
Interesting - currently laid up with a cricked neck and almost terminal self-pity, so I've some empathy here. Leaving aside its usefulness as a lightning conductor, the wheels look a bit small - I reckon something about 12 inches with balloony tyres would be less inclined to hook on all those little sticky-up rocks and would jar less on the downhill - although it might push forwards a bit more on drop-offs.
For 390 euros, you could certainly knock up something yourself. Poles are easy to come by, there are masses of second hand 'off road' pushchairs out there, and chest harnesses are around in plenty of French outdoor sports. Fifty quid would probably cover it, although I suspect you'd spend a lot more just tweaking it.
Best bet, though - find a sympathetic partner who'll carry the lion's share of the gear. You seem a decent human being, so shouldn't be a massive problem.
Martin