Next level of the Youth Fruit quest?

I’m looking to ultra-evolve one of my monsters for the first time. I have almost all of the ingredients. But I need to train it to max first. I need de-aging fruits for this.
The Youth Fruit quest under the “Ultra-Evolve quests” section shows me only one level: "Lv. 1 Youth Fruit"
It’s very easy but yields very few basic-level de-aging fruits. How do I get to the higher levels? I need more/better Youth Fruits.

the only next level youth fruit is from a “level-up” event that occurs ever so often… other than that you cant upgrade the regular one.

they should increase the limit size from 10 to 99

In dungeons on online mission, Grunt give a fruit With a low probability.
You can get both exp and fruit.

I would say 25 max 99 is a little much.