I randomly stumbled across this on Facebook thanks to sponsored posts. Normally they're annoying and useless, but once in a while a good one pops up. This counts as such. A random t-shirt website has created 49ers-themed superhero t-shirts.
I can't vouch for the site nor the quality of the t-shirt material, so you'll want to do some googling, but the concept is pretty cool. They take pictures of various superheros and give them a 49ers look. The Hulk one pictured above might be my favorite of the group. Of course, Iron Man is the most natural fit given his existing colors.