Help alternative milk at end of breastfeeding journey

So my boy is almost 10 months and flying through my milk supply faster than I can pump at work. He is sensitive to dairy so I can’t switch him to normal milk and he already gets constipated with breast milk so I don’t think a transition to formula would be wise and even if I did it would have to be dairy and soy free. I’m just wondering has anyone tried the other milks earlier than 12 months. The dr has recommended whatever kind of alternative milk he likes at 12 months.