Hi, I am looking nut haven’t found a n answer as to how to create a nostalgic pet.

You'll need to get a nostalgic (pet species you want) instructions and take them to Vanya. Then he'll ask you to do a little quest for him. When you return with the requested items he'll turn the instructions into a toy. Then you take the toy and an back to him and he'll change your active pet.

Thanks so much , I appreciate the assistance

this is also answered in the FAQ (subeta > help > FAQ).