Stoma too big

Hi everyone,
I’m looking for some advice.
My stoma measures approximately 120mm wide and 50mm tall, and I’m having a very hard time finding an ostomy bag that fits. So far I’ve only tried one-piece systems, and the largest opening I’ve found still seems too small.
Because of the size and shape of my stoma, I’m worried about getting a proper seal and preventing leaks. I also don’t currently have insurance, so I’m trying to find affordable solutions if possible.