Not seen that one before, but really it depends on what you are using flash for and where.
The cheapest cost effective option is the ABBC (a better bounce card), Fab Foam from Hobbycraft or Funky Foam from Range stores (range being cheaper).
The Fong type are ok in smaller rooms or close up, and some people swear by the Stofen but i've not used one.
Dont forget that you can manually zoom the flash to get different effects similar to using a diffuser, i.e. the diffuser spreads the light and you lose some of it, you can manually zoom the flash head out to 24mm and put the wide angle attachment over to spread it further.
Thats assuming the 430 does manual zoom. Personally in rooms with white ceilings close by bouncing with abbc throwing some light forward works well. If there's no ceiling say outdoors then a diffuser will tone down the harshness a bit, but you are better then taking the camera off flash a la Strobist.