You should try Staples, Walgreens, Office Depot, Office Max, Fed Ex, UPS, , Kinko's etc. to name just a few places. But, I would suggest that you telephone them first, as the personnel there work on many different types of projects on a daily basis, to include all the necessary devices and materials needed to perform these jobs, i.e. cables, usb cables, etc. And they should have no problem answering any of your questions, or perhaps suggesting an alternative . You can also call each of them to find out who has the cheapest prices to fit your needs. A phone call is all it takes.
Another place you can try is your local library