I was able to get E to take Nutramigen by flavouring it with Strawberry Nesquick. I know that sounds insane, but it was recommended by Neocate when I called them. They do offer flavouring packets, and if you google neocate and your country you can give them a call for a sample pack. I needed it to be fixed right away so they suggested the Nesquick while we waited for the flavouring packets. I have no idea if there is anything in there your lo can't have but it contains neither dairy, nor soy, nor strawberries as my lo has intolerances to all three. I was able to wean her off of the flavour before the packets arrived in the mail and even now at age 25 months she loves the formula.
Have you tried warm/tepid/cold temps? I had to heat Nutramigen very warm and do some good skin to skin cuddles with E. I also fed to sleep as was her routine for a million reasons and I found the more sleepy she was, the more likely she would be to take a nice warm cuddle with a warm bubby.
Best of luck. The stuff really is gross, but they need it and I know it's hard.
Hugs