What is the ruling on delivering a sum of money in a specific currency in one country and receiving it from another merchant in a different country in a different currency with an increase over the market price, in exchange for bearing the risks of travel and the desire to obtain this increase? And what is the Shariah-compliant alternative to this?

Currency exchange (sarf) requires hand-to-hand possession, based on the hadith (definition): "If it is hand-to-hand, then there is no harm; but if it is deferred, then it is not permissible." The transaction mentioned is not permissible unless the merchant provides a certified check in lieu of the currency, or if the exchange is conducted over the phone with both parties taking possession at the same time. As for the currently practiced method, it is not permissible. However, it is permissible to use a "suftaja" (bill of exchange), which is when a person lends money in one country and receives it in another country in the same currency due to fear of the journey. This is permissible when there is general fear.