I've used
www.mapleleaftickets.com in the past, has have many other DIS members
I'm not sure how they compare, pricewise, at the moment, to other sites as I haven't had the occasion to check out prices this year.
I've ordered tickets to be delivered to the UK, ordered them and collected them at their office in Kissimmee and also just walked in off the street to buy them with no problems whatsoever.
If you have any questions they are more than happy to answer e-mails quickly too