Sleep Positioning help

I discovered my daughter had severe acid reflux when I found her unable to breathe while laying flat. Luckily I found her on time, and is is okay. Since then the diagnosis was confirmed, she’s been on medication but still is unsage to sleep flat in bed. She sleeps well elevated in an infant car seat. I put her Angel Sounds breathing monitor (bought at babies r us) underneath her back in the seat and add plenty of padding to the infant car seat at night for comfort. I need a new solution now though as she is 8 months old and will be outgrowing this seat. Elevating the head of the bed was never a good option because she would roll off and into a flat position. I did receive a second hand toddler front facing carseat but the baby would be sitting straight upright versus at an incline. Anyone have any solutions???? What do you do?? Any reply could be helpful so please don’t hesitate.