babies and car seats and taxis

so every day I take my three month old to go pick up his four-year-old brother and I take the bus going and a taxi coming home because my four-year-old is tired after school and doesn’t want to do the walking and I prefer not to fight with a four-year-old lol but the 3 months old is starting to get bigger and I’m curious what I could do when it comes to the car seat because soon he’ll be able to sit in the stroller and doesn’t need the car seat but taxis over here in Buffalo are very strict about the car seat and literally won’t take me if I don’t have one so what am I supposed to let him ride in the stroller and carry a car seat in my hand every single day?