Without the actual devices in your hands, the only options are to use application-based emulators like Adobe Device Central or websites that use virtual emulators or take screenshots from mobile devices. Unfortunately, neither option is as reliably accurate as a real mobile device, so you can't totally trust them. Ideally you should try to find someone you know that has the device you're looking for and ask if you can use it for testing.
There are some online services that show your sites looks on a screenshot of an iphone/ipad, but they're not 100% reliable. The best solution is just to borrow an ipad or iphone from one of your friends.