The "custom font" mechanism petrib suggested requires the use of Canvas, so you cannot use this on a Form. You could consider switching to another U library such as LWUIT, which I think will allow you to use a custom font.
Think also about input... a non-Urdu device will not provide support for Urdu input either.
My point was: if a user has a device that does not support Urdu, presumably he is comfortable using the device in English. You can provide English only for these devices, and Urdu for devices that are capable of supporting it. Some devices simply will not support Urdu without you doing a lot of work.
to find out the language and/or region for which the device is configured, and you can select the appropriate language text automatically.
Will give you "en" for English, "ur" for Urdu, etc.
String language = System.getProperty("microedition.locale").substring(0, 2);