Picked one of these up from the PoundLand at Leeds St Johns Centre, they had a whole stack of them in different colours.
A grip and powered speakers for your DS Lite. "The comfortable Sound grip for DS Lite provides additional grip and gets the very best sound out of your console."
£7.99 at Amazon (~£15 if you buy from marketplace sellers!)
My monkey paws get painful and cramped if they're wrapped around a DS for any length of time, this gadget expands it out to more of a console controller shape and is way more comfortable to hold. Not tried the speakers, they take 2xAAA batteries, I don't expect they'll be amazing but they'll probably be adequate.