My Mosquita got a new housing as described in this post. As you can see, there is still enough room for a memory morse keyer.
I found a really neat solution in the JackYack created by Jack, AI4SV. It consists of only 12 parts and a programmed ATTINY85 microcontroller.
This keyer provides enough features for a portable and fixed operation. a complete list can be found in the PDF document.
I've ordered three boards from OSHPARK. This how the integration in my Mosquita looks like:
I replaced the onbard piezo buzzer with a 10k pot and used a 5nF cap to couple it into the AF path.
The complete schematic for my Mosquita:
One is inside my Mosquita, the other two are available, fully populated and tested.