the wurforper 361lp , with its smooth barrel insert looks like it could be used in the leuchtpistole 42. I have heard there was a rifled kampfpistole version of this also , but has any one heard of a folding stock and sighting device for the LP42? I’ve seen pics of LP28s used without sights but how could you possibly hit anything like that? remember the LP42 was the later stamped flare pistol not the earlier machined alluminum , zink , or Z marked steel LP28 which could be fitted with sight and stock
If my memory is accurate, (and I’d have to dig out the book, and I do mean dig), what you’re apparently thinking of is the panzerabwherwaffe adaptation of the Signal/Flare pistol.
In rough terms, think “mini-panzerfaust fired from a Flare pistol”.
There was a limited number actually produced (approx 200, by memory), despite the usual late-war orders for vast numbers, that were not met by production.
The device fired a hollow-charge grenade to a distance (from memory) of 150 meters. The device was equipped with both shoulderstock and adjustable sights for both direct and indirect (a-la mortar style) fire.
I hope the info helps.
Regards, Uyraell.
Thank you, My Friend 
reliable as ever
Warm Regards, Uyraell.