Is it permissible to leave a small amount of money from the salary deposited in a usurious bank, using a Visa card, for the purpose of booking travel tickets electronically, given that Islamic banks in Egypt do not provide this service?

The basic principle is to avoid dealing with usurious banks, even in permissible matters, unless there is a need for it. This is because depositing money in them, even without taking interest, is considered a strengthening of their position and an assistance in their falsehood. Therefore, if there is a need to book tickets with a Visa card and booking through traditional methods is difficult, then there is no harm in doing so. Otherwise, the general principle is to avoid dealing with usurious banks altogether.