The Socialist Jr. does the "Brutalist Jr. thing" but with a number of improvements and additional options built right into the PCB. If you're planning on building a highly modified Brutalist Jr., the Socialist Jr. will get you there faster.
The pcb has the dimensions 86x47mm. It comes along with the original 3PDT utility pcb.
Here you can find a ready to solder kit:Socialist Jr. kit
Here´s the build documentation: