A company called 500 Level is producing some fun NFL t-shirts featuring a variety of players, and several 49ers are among them. They have t-shirts for Michael Crabtree, Colin Kaepernick and two of Patrick Willis. They have gone through the appropriate channels with the NFLPA, and so these are officially licensed to sell this merchandise.
In order to help fund their company, they have created a Kickstarter campaign. Through Kickstarter, people can help crowd-source financing for various projects. Through Kickstarter, a group sets a goal in terms of dollars and a date. People pledge money toward that goal, but are not charged unless the group meets their goal.
In this case, 500 Level has a goal of raising $20,000 by August 28. They are currently at $11,210. If you pledge $20 or more, you can get one of the t-shirts. If you pledge $15, you can get little kids' versions of their shirts. If you pledge $10, you can get an art print of one of the pictures. Again, if you pledge the money and they do not meet their goal by August 28, they will not charge your credit card.
They offer the four different players in red, white, light grey and dark grey. They recommend you get a shirt a size larger than you would normally wear. Here are a couple examples: