I would say thats quite unusual so your prob best off building something yourself. Wouldnt be hard I would imagine just make sure all walls of both tanks are supported, ie add a center brace onto a normal tank design
How do you want them arranged? Stacked or side-by-side. For the stacked look, you can buy a heavy duty bookcase (just check its weight capacity); for the side-by-side look, there should wide tv stands that could handle the weight of 200lbs.