Just ask him already. Neither him, nor you want to have an embarrassing accident in his place because every time you or he walks by the scene of the accident, it will haunt you two forever! Y'all don't want that.
My ex-girlfriend sent me to the store to buy her some pads once, it was weird feeling but I'm still here and still a man. Besides feeling uncomfortable, the only other thing that bothered me was all of the choices! There are so many for a novice to choose from. My advice to you is to tell him your problem and instruct him on exactly which brand and variety to purchase. If he can't handle the pressure, ask him to seek help from a female acquaintance of his. Maybe he can ask a neighbor to lend you a clean, unwrapped one? Sorry if that's against some female code I know nothing about. Either way, act now if he is your only hope or wait for mom if you can?