airport card problem not installed

hi whenever i use my mac if i put it in my school bag to take it somewhere it will always disable the internet card when i go to use it saying its not installed i try then if i just nudge/ tap it the internet card will die im woried and its unable to be fixed. is it possible to get some form of usb airport devise to connect to my internet router at home like a usb that acts like a airport card so i can connect to wireless networks with a rough price or link

thankyou in advance i need all the help i can