I make big jigs all the time.
My biggest jig is 48oz.
But 12-20oz are quite common for me.
Most of my big molds are custom CNC molds.
Bigger custom molds are not cheap though.
I've paid upwards of $300 for one to get what I wanted.
There just isn't enough of a market for Do-It to make many large molds.
Depending on how many you need you might consider buying jigs or buying blanks and painting them.
To make the big stuff your going to need custom molds, custom fluid beds, larger ladles, a big toaster oven etc.
It adds up fast.