Where can I find a GWAS data set about genotypes and phenotypes for Zebrafish and rice?
I think it will be more productive for you if you choose one of the public human datasets and practise your GWAS methods on that. A couple of examples examples:


1000 genomes -- use "population" as your trait of association. You'll find that you get association across the whole genome, so the analysis method would change from "what bits are associated" to "what are the bits that are most consistently associated"
NCI Genomic Data Commons -- open access (and controlled access) data associated with cancer