Crafting Festival Merchants will help. They are more efficient mana producers than most of what you have, other than the Somnial Pool (and Tender Tag Team if you upgrade it to Ch. 10).
The Simmering Soup is a daily prize in the Mama Juul's Fusion Feast event, and will be available again on the last day of the event. It's as productive as your Somnial Pool, so it's a great one to have.
Upgrading your Mana Plant & Gum Tree to Ch. 9 and/or 10 will switch them to mana production, and although tiny, they are some of the best mana producers per square.
In a pinch, the Arcane Library can be built very early on in the chapter and can tide you over until you get your hands on some better options.