superbrightLEDs worked great for both of my clusters. Cost me $16 shipped for 6 of them and they delivered in 2-3 business days.
They are polarized - so in one direction they work and if flipped 180, they don't. There is a little white dot on the plastic base - if that is pointing at between 1-2 o'clock (looking at the back of the cluster) that should be the right direction. I pulled the little metal contacts up a bit before twisting in to insure contact...
On the Wagon I pulled the green diffuser out and glued in a scored piece of clear plastic...I used the white bulbs - I love the way it looks...bright enough to see but not too bright that it's distracting. The dimmer works a bit too.