Oh lordy… this depends on whether or not you want to spend $10 bucks or $100 bucks… I got a new one for my RPi and I’m grateful that I got it. Why? My Windows box doesn’t have the drivers for the wireless card that I use for my Linux’s box, installed properly that is. My mind remembered that I got a external wireless card a while back (sold my RPi) and on top it all, I got a disk for it that install the proper drive. Yay!
What’s the moral of this story? You don’t need a fancy wireless card to use monitor mode or use it on your Linux box. I believe mine cost me roughly, $10. If anyone/you are wondering what it is… it is, USB 2.0 Wireless 802.IIN which comes with the disk that installs the driver RT5370. I also got it off of Amazon. I suggest personally… look on Amazon or places like Walmart for a wireless card and check out the compatibility drivers for Aircrack-ng.