As a replacement of USB cable, you can install Android SDK and it is capable to find ST (as an android device) via WiFi and show all files on it. You can use this to put books on it much the same way as through the USB cable.
As for going an extra length to be able to buy ebooks from B&N directly (like geertm suggested), it works too. But why bother if they don't want you as a customer? Also it is always good to remember that >90% of money you pay for ebooks stays in the pockets of the publishing houses and b&n and only <10% goes to the author.