Best Indonesian SIM Card for a Short-Term Visitor?

My cousin is visiting Indonesia for two months over the Christmas holidays. They'll be using a phone purchased overseas and want to avoid registering it, as their stay is temporary.  They're wondering about the best option for mobile data during their visit.  Can they use their foreign phone with a local SIM card for this duration?  Should they get a SIM card specifically for foreigners, or is a regular Indonesian SIM card an option? They have a passport but no Indonesian KTP (identity card).  Many visitors find that purchasing a local prepaid data package offers the best value and convenience for short trips.  Providers like Telkomsel, Indosat Ooredoo, and XL Axiata offer various packages to suit different data needs.  Some even offer eSIM options, allowing for quick activation without needing a physical SIM card.  Alternatively, international roaming might be considered, but this can be significantly more expensive than a local SIM card.  Ultimately, the best option depends on their data usage and budget.  We've decided on a solution where they'll either get a roaming data package or we'll 'barter': I'll get an iPad in exchange for buying them an eSIM for their phone while they are here.  This seems to be the most cost effective solution for both of us!