The Best Buy website accepts Paypal. If you have a paypal account, you could always load the card on, buy the eShop card from them for $20, and choose Store Pickup and pick it up at the store.
I would do that, except that the nearest best buy to me is about a 2 hour drive, paypal is acting up currently and won't let me add funds so until that's all sorted I'm just going to go with a straight trade.
Paypal is acting up for me too by the way. I'm trying to look where you can add prepaid cards as I never knew Paypal had prepaid cards and the site keeps giving me error messages.
Ah, ok. Now that I think about it, I may have seen those cards before. Seems like a weird thing to have but I guess it has it's uses. Thanks for the link.