The easiest route is to bring a car seat with you, since Bali does not have a reliable local market for them and rental cars almost never include one that is properly installed and up to safety standards. Most airlines allow you to check a car seat for free in addition to your regular luggage, and many parents use it in the terminal as a stroller substitute for a toddler who won't walk far. If you already own one that fits your child's current stage, packing it saves you from a scramble once you land.
If bringing one isn't possible, start with the big supermarkets and baby specialty stores in Denpasar, where you can sometimes find imported car seats and boosters, though stock changes often and imported gear tends to sit at the pricier end of what's available. Before you buy anything secondhand at a market or from a classifieds group, check the manufacture date and look for cracks or missing straps, since heat and humidity break down foam and plastic faster than in cooler climates. Whether a car seat is worth prioritizing at all depends partly on how your family gets around day to day, which is worth thinking through when you decide on a car or a scooter with kids.
Private drivers and airport transfers rarely carry a car seat unless you ask well in advance, and even then the seat they provide may be old or an odd fit, so confirm the exact model before you rely on it for a newborn or infant. Some long-term rentals include a family car as part of the deal, so it's worth raising car seats directly with your host when you arrange a long-term villa rental. For everyday baby gear beyond the car seat itself, the same stores that stock western baby products are a good place to start looking.
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