What is a excellent third party memory to buy for the 2011 mac mini computer. I need 4 gigs . Thanks

Any brand will be fine, Hynix, Crucial, Patriot, Corsair, you name it, just make sure the RAM you buy is compatible with your Mac (you have a MBP if I remember well). If it is a pre-2011, you'll need 1066 MHz, if it's a 2011, then it will accept 1333 MHz and the next models will have 1600 MHz wooohoooooooo!
PS: we have a partnership with Crucial so sometimes you can get a discount when it's advertised on the website.