To be precise, "Gomamon" is a fictional Digimon character (a seal-like creature) from the Digimon franchise. A "Gomamon-trainer" would refer to a human character (like from Digimon Adventure ) who partners with and raises Gomamon.
Since this is a very niche, fan-oriented term, there are likely specifically titled "Gomamon-trainer." However, you can find relevant papers on related broader topics. gomamon-trainer