Well back when I played Tau in 4th Ed, I had tons and tons of extra missile pods. It would be really cool to glue some of the missile pods together, shaved down the nubs for attachment, and make a little 9 pack of missiles(very Mechwarrior-esque), I think it would look super righteous.
I think the Valk rocket pods are too big. Another opion might be to take some plasticard and make some boxes, drill holes in the form of a rocket pod(the warheads don't have to poke out). That also would look really good, and you can make them as big, or as small as you want. You have tons of options. Keep us updated once you figure something out. I'm curious to see what you come up with.