Replacement power cable for Mindstorms RCX
The cables you point out are newer Power Function cables and are ill-suited for 9V usage such as with the original Mindstorms kits. Technically, you could daisy-chain two of them and it would work, but that's probably not the best solution.

Here is a bigger illustration of the cable, courtesy Philo:



You can clearly see that only one end of the cable has a 9V connector on the bottom.

I would advise you to check Bricklink instead, you should find plenty of seller there, possibly in your own country.