Have checked out Dakine,K9,Chinook but no luck finding the ones I am after.
They are a flat bit of plastic that one side has a round series of teeth with a screw hole in the centre and at the opposite end on the underside has a locating tang that inserts into the unused screw hole.
Hope this makes sense.
Anyone know who makes and stocks them.?
They sound like the Starboard anti-twist ones. Try your starboard dealer or Auswind (wholesaler)
Yer agree with Sausage, sounds like the Starboard 'K9 Anti-twist plugs', I just got some recently from Auswind, they were really helpful 
Or just an idea if you can't find them / can't wait
spread some Neo-Rez wetsuit repair goo on the bottom of the footstraps where they will contact the board. Let it dry well before screwing the straps back on though!
it sets rubbery and sticky - really resists the twisting once it is pressed down hard onto the pads
I find mine don't twist, just using the rectangular washer with teeth under the screw head (not under the strap, that may be bad for board cosmetics 
haha)
but the Starboard thingy described above is very good - wonder why other makes don't use it also
haha)
