heres the cheap toner, it's an amazon bestseller so you should have zero issues
GREENCYCLE Compatible Toner Cartridge Replacement for Canon 126 CRG-126 CRG126 3483B001 for use in ImageClass LBP6200d and LBP6230dw LBP-6230dn LBP-6230 Wireless Laser Printers (Black,2 PK)
(i checked the forums and this printer accepts 3rd party toner, zero issues)
printer is also on sale at bestbuy if you want to pick it up local, pretty sure they won't sell cheap toner tho
you should also think about getting a case of paper tbh if he's doing lots of printing
comes out to less than 5$ a reem, staples would try to get 8$ a reem for hammermill
and if you don't use it all, it's paper, unless you decide to store it in your basement to grow mushrooms, it'll last you a while, it's not really that much paper if you think about it, a textbook is around 500sheets, thats already 1 reem