Looks like a very few copies of used F-Zero Climax cartridges are being sold on eBay (I found four of them). You know, just search F-Zero Climax on eBay (I cannot post links now as I just joined the community).
Luckily enough, two days ago I managed to get an used copy in good conditions, with manual and box, for 45.50 USD (+ 9.00 USD for shipping). I hope it wil arrive soon, I really can't wait. You should really buy a copy of this, it's getting dangerously rare. 