I'm assuming if you're staying off-site you'll have a car at your disposal. I believe that you can still buy from
Undercover Tourist and use their Orlando Pick-Up location.
http://www.undercovertourist.com/united-states/florida/orlando/attractions/tickets/pickup.html
It sounds like you just have to give them 1 business day's notice.
If you're not familiar with
UT, just do a search for them on these boards. They're pretty trusted by a lot of people here at the DIS.
(Not only do I not work for them, I've never used them myself as we buy AP's through Disney to get our DVC discount, but I have heard a lot of good things about them on these boards, and I have friends who have purchased tickets from them and they had a smooth transaction.)
eta: Oh, and have a fun trip!