I set up my own over flow, the tank was drilled for me but I have drilled tanks myself before and it is easy, just did one with Pies a couple of weeks ago for his fresh water, 4 holes.
if you contact Pete at port nick glass in petone, he charges around $1 per liter to make a custom tank, he makes stands to but not sure what he charges. i would use a shop as a last resort they will charge 2-3 times as much, Pete supplies most of the shops in the lower north island. he wil deliver to u as well.
once you know what you are doing with the over flow the hardest part to sort out is the over flow box