Illustrator is the go to. But if you already don't know how to do it yourself, it would probably be 100 times easier to pay someone to draw you one.

Thank you, I guess it's worth me learning how to use it because I want to have multiple t-shirt, gi patch, hat, etc. designs as part of a business I'm building.

Honestly, unless you have a talent for and a real interest in graphical design, don't bother. It's like saying you need to learn how to use a paintbrush because you are in need of a bunch of great looking paintings. Something like crowdspring.com is a much better investment of your time and money to get a professional result.