You might want to wait & do a ground up build. Then it can look something like this first prototype. This weapon's receiver is 1" shorter than an M11/380 or M12 & the barrel externally is 5/8" shorter.
Right hand view
Left hand view
Right hand view with Sten mag for size perspective
Left hand view with Sten mag for size perspective
It shoot's, so parts kits will be available in about a month. These parts are not fully compatible with Leinad M12s. Fully assembled guns will be available in 6-8 weeks.