metric Allen keys
metric Allen keys (aka hex key)are available even in US and A 
The auto (and other motor) industry use metric.
From memory you will need 2.5mm Allen key for the grub screw of the Valley skeg slider
hex wrench
After the little learning session with the metric hex wrench, I stopped at Lowes on the way home and bought myself a fold-up set that holds wrenches from big to very, very small and bought the husband one, too.
It is now in my repair kit.
As an addendum: the husband has metric tools but nothing small enough to fit the 2.5 screw.
Park Tool 2.5mm Hex
I happened to have a nice 2.5mm Hex wrench in my tool kit from a Bondhus hex wrench set I purchased for working on bicycles. However on several occasions I have often found it difficult to exert enough mechanical advantage using the rather spindly 2.5, particularly when you have to grip the short end portion of the ‘L’ shaped hex wrench with your fingers. This is particularly true when trying to get at the 2.5mm set screw on a Valley kayak’s skeg control slider. In looking for a better ‘tool for the job’ I came across Park Tool’s T-handled 2.5mm hex wrench (ironically another maker of bicycle tools). This looks like the ticket. The next time I place an order with Amazon I am going to pick one up.
http://tinyurl.com/2cldolj
New slider design makes no sense to me
I have been using the new design (black plastic piece with the four screws by the knob) for about one year now and I do not think it’s easier to repair or adjust when comparing to the old design - my experiences are totally opposite.
It seems that the skeg cable tubing shrinks and expands quite a lot when the temperature changes. Last summer my skeg cable length was exactly correct but when winter came I noticed the skeg would no longer go all the way up. I inspected the assembly, found nothing wrong, and assumed that the cable tubing had been badly seated originally and had now settled in where it should be causing the cable seem too long. The only solution was to shorten the cable and everything was ok. Now, when temperatures are back to summer temperatures I noticed that the cable is too short, exactly the same amount I shortened it earlier. The slider will no longer go all the way forward and the skeg will not drop as far down as before.
The old design allows adjustment of the cable length by the slider knob and the extra length of cable will not cause problems but the new design doesn’t allow this as the end of the cable no longer goes thru the deck as it does in the old design. The only solution for me is to live with it or to have separate winter and summer skeg assemblies.
I’m also somewhat sceptic that the new design will withstand the stresses involved when water in the space between the deck and slider assemby freezes without room for expansion possibly causing damage. Last winter I have been very careful and always let the assembly drip dry after usage - something that was a lot easier to do in the old design (and freezing water would not damage the old desing anyways).