What's a good formula for bad reflux?

My 10 month old has EXTREMELY bad reflux. It went from spitting up to now vomiting pretty much everything she takes formula wise. She has Trisomy21(Down Syndrome but we call her our UP syndrome baby cause theres nothing down about her😉) so she does have feeding issues with baby foods and formula she has oral/speech therapy starting on Monday though. She was on Gerber Good Start Soy then at 9m switched to Gerber Good Start Soy3 for more protein were she vomits everything. She is on Nexium in the am and Zantac in the pm and small amount of oatmeal in her bottles. All of this told by her Pediatrician. She has another G.I appointment in a week last time she was seen there was a few months back b4 she had heart catheterization surgery and open heart surgery and he put her on Nutramigen which most definitely didn't tolerate well and came back up faster then swallowed it. No swallow issues passed 2 test. Can anyone recommend a great formula I could try for the week until she's seen by the G.I specialist? I'm desperate for her cause she's losing weight (not drastically but she is) her pediatrician just said to keep her on the Soy3🤷‍♀️. What do I do?