The custom t-shirt meant here is one that is made 'just for you' as opposed to factors produced 'one size fits all' tariff that is more commonly found in stores. The custom t-shirt in question is the one that bears the message of your choice; perhaps a message that indicates what you stand for. It could be a t-shirt you are looking to use in a particular event (so you get it to show it in mind).
Well, there are several ways in which you can go about getting designer custom t-shirt. In other words, you should be prepared for the crowd quite a bit, if you get a custom t-shirt in this way. And since this is a t-shirt that is the essence of human labor requires immediate application, you should be prepared to pay a price that is pretty neat for them.
Alternatives to go to a clothing store brick and mortar will be adjusted online stores that promise to help you 'design your own' custom t-shirts. This arrangement is that the online store will provide you with software programs through which you can determine what you want in terms of t-shirt: the desire of making software, one would say.