For a standard credit card and coin-sized pouch, use these general dimensions:
iThinksew has a fun pyramid-shaped pattern that stands out and is great for holding small trinkets. Pattern For Zippered Coin Purse
Two 5" x 4" pieces for the exterior and two for the lining. Zipper: One 4" or 5" nylon zipper. For a standard credit card and coin-sized pouch,
Crazy Little Projects offers a simple rectangular pattern perfect for cash and cards. Pattern For Zippered Coin Purse
For a unique shape, SewingTimes provides a detailed video tutorial on making a round coin purse in two sizes.
Two 5" x 4" pieces of fusible fleece or interfacing for a sturdier feel. Top Free Patterns and Tutorials Here are some of the best specific patterns available: