I am a huge fan of the Korg Monotron Delay. It is my favorite little gadget. I own it as well as the Monotron Duo. But I don't have a Stylophone!
This seems to include some similar features of the Monotron Delay by having delay, the LFO (square and triangle), and a filter.
But what this adds on top of the Monotron Delay though is an envelope and resonance, Sub octaves -1 & -2, and PWM.
And it has a touch strip in addition to the stylus keyboard.
Estimated release is not until May though.
You can register to preorder and get 20% off (with no commitment to buy):