13 week old product recommendations?

My 13 weeks old (3 months and a week) HATES being on his back all day long. He only tolerates tummy time for about 5 - 10 minutes at a time bc of his bad reflux. Soooo, should we get a baby seat? Or a exersaucer? He has VERY strong legs and kicks all the time. And he can't use a bumbo bc he legs are too chunky! 😂 thoughts? He has good head control but can't sit up by himself yet. He still tumbles over. 😂😂😂😂 thanks y'all!!