I could not find this game for the NES. I think you mean the SNES game. SNES ROM expanding is really easy to do yourself or you could use a tool like lunar-expand https://www.smwcentral.net/?p=section&a=details&id=31275 to do it for you.
For NES this could be a bit more complicated depending on how the game handles banks swaping and you need to do it manually.
You probably filled up a bank and would need to change some bank handling related data or write extra code to have text data on other banks. Not sure how familiar you are with coding tasks on the consoles. Feel free to share resources. Personally I would paste everything in a ASM file to patch with a tool like asar since it is much easier to understand what your are doing in my opinion.
