It all depends on what you want to pay for one. In a quick Google search of "Banzai Run for sale" there are at least a half dozen retailers with one. They are all at least $4k though.
Also, if you go to pinballowners.com and look at the registry for Banzai Run, there at least 4 or 5 for sale and many more that say "maybe" they would sell. Contact all of them and see if one would sell for what you would like to pay.
Just some suggestions.