HI,
I was at Manny's few years ago, when the owners talked about their in-house made Gefilte fish. They had visiting deli owners from New York who did not make their own Gefilte fish. They were quite impressed Manny's did.
If this applies to other delis, you may want to inquire if they make it in-house or is it a third party vendor.
I don't know quite where you hang your hat. If it is near Springfield, I would call Carter's Fish Market to speculatively inquire if they make some. If they don't, they could still prep fish for you to make it yourself.
Carter's Fish Market has a shack in front, which fries fish to order. This might be seasonal, noting my visits have always been in summer. They also have a retail fish market immediately behind.
Address: 1900 S Grand Ave E, Springfield, IL 62703
Phone: (217) 525-2571
I would suggest you call a local synagogue to learn what the locals do. There are at least two synagogues in Springfield, IL.
Good luck!
Regards,
Cathy2