Not a good plan...
Macerators move waste at 12 gpm...you can't pump fast enough to keep up with it, which results in fried impellers. If you try "pump some, run the macerator some," it MIGHT save your impellers, but it's more trouble than it's worth and result in a backup if the macerator fails. If you want an electric toilet, buy an electric toilet. The best "bang for the buck" in electric macerating toilets is the Raritan SeaEra. http://www.raritaneng.com/products/toilets/electric/sea_era.htmlAs for a tank...your best source is Ronco Plastics: http://www.ronco-plastics.com They make top quality rotomolded tanks for a very reasonable price and have more than 400 shapes and sizes, over 100 of which are non-rectangular. And the install fittings in the sizes and locations specified by the customer when they make the tank. You might also check out the link below before starting this project.