Go to www.knittingpatterncentral.com and look under the heading for "Animals," then look for the one called 'Fish.' You may have to adjust needle size and yarn to make the fish small.
I would look at a picture of a goldfish and knit accordingly. Cast on for the tail and increase/decrease to make the shape. You could use some of the new fancy yarns.
Lion Brand Yarns has a small crocheted one; they may also have a knit version, as they often provide both types of directions for their projects. You may have to sign up to receive the directions; but they have a lot of wonderful patterns for free, so it is definitely worth it.
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