Jaycar and dicksmith sometimes carry a 3 set partylight version , and a single party light that moves around with a small electric motor included.this is similar to what u have mentioned in the post/ batlight website...
each light is about the size of a coffee mug.
If u go to jaycar or dick smith, get their catalogue and go thru it...i had a similar idea when i first got my batman forever but i just never found the time or the spare room on the roof.. it would look bloody great...but definately go to jaycar/dicksmith and get their catalogue...u could easily place the bat shape over the lense of the light n modify easily that way.
their respective catalogues have alot of stuff that is not sitting on their shelves.hope it helps.