How can I spoof user-agent on an Apple mobile device browser?

This is related to securing an application on a corporate network against certain types of access from personal PCs and mobile devices. Specifically we are able to require authentication from the users so we do know who they are. The current ask is just to block access to parts of the application from a mobile device. The application relies on the user-agent string to determine if it is being accessed through a mobile device. Is there a way, on a mobile device (e.g. iPhone, iPad, etc.) to spoof the user-agent string and if so, how would that be done?