It is important to know if this is your main source of income or something you do for additional income.
In sports apparel there are "seasons". You can cold call till you are blue in the face but it will not solve the issue you are facing and could make it worse. First you need to get to 100% + capacity in season. If you are there then you need to learn how to increase off season business. If you look at most dye sub sports apparel companies, especially cut and sew shops, they offer jerseys for a range of sports. Many that focus on a single sport will sub out their work so they do not have the expense of capital equipment. Some of the largest sports jersey sellers, especially in softball, do not do their own work.
You are left looking for markets outside of the typical softball jersey buying season or expand your offerings. One that has been incredibly successful for us is dye sub custom lawn chairs. Although we market specifically to our customers we get orders all through the year. The great thing many we do now have nothing to do with the team and are just personalized for an event or special occassion.