^ Metroid hats are a really good idea.
I'm just not sure if it would help sell the sites brand, label etc.
If that's one of the reasons they wanted to sell for the site, I'm not sure.
I think shirts would be quite effective but it depends on the design, and if you plan on selling both male and female tees.
Shirts can be confusing though, I hope you find a t-shirt making company that could give you a nice deal.
The second and probably more favorable option (for me anyway)
is selling baseball hats with the MDb logo.
Both genders wear them so you have less product to buy and you'll save money. Hats are also easily visible and might draw more attention.
Sorry if I keep blabbing on, I took a marketing class and I just want you think critically of how you achieve this.
I'm sure you'll do fine.