Is it possible to buy a Transponder at anytime during the day or only during certain hours? We will be traveling through around 6:00 a.m. and need to buy one.

The tollway shop has hours. Not 24/7. Try looking online.

Only during the business hours that the toll way office is open at the oasis

Add the app 'FastToll" to your smart phone. I just used it on Saturday and paid my tolls when I got home. Works great! The app must be running when going through the tools.