If you go to this site
http://precisionturf.ca/products.php and click on Products and then click on Product series "B" you will see some designs as well as a filling meter that comes in handy. You can make the tank up in house if you want. Ag dealers usually have a variety of cone bottom tanks, just ad a pump and agitators and you are good to go
I have a 750 gallon tank with 2X1,5 HP pumps and the filling meter. I just throw the required product in the mixer to complete all fairways and then meter out 1/3 of the mixing tank into the sprayer tank and top up with water. It speeds up the spraying time immensely. I have the 750 mix tank plumbed into the irrigation system and can fill it in about 2 minutes. The transfer to the spray tank takes about 5 minutes.
If time is of the essence, a mixing tank is a great addition