Sanctioned events generally require authentic Magic cards (with limited judge-issued exceptionstypically only if a card is accidentally damaged during the event)
Theres also Best Buy, but its display is still marked as "Coming Soon", usually because it drops products right at launch
Then, when it's time to close out after drawing your deck, you can finish them off
The bigger shops with the most turnover are going to be the best bet to actually find things you want, but the price you will need to pay is going to generally be far over what youd find it for online
Raid When this creature enters, if you attacked this turn, look at the top three cards of your library
These boosters usually have at least a rare and a foil in each pack and are slightly more expensive since the cards themselves are staples of Constructed decks across multiple formats