Easy as this, if you have a lighter S or other tracer unit you can friction fit it to the MP5. Pull the original flash suppressor off first.
I’ve used about 8 cms of 20mm conduit to act as the adapter. The conduit fits snug over the outer barrel, the tracer friction fits in the opposite end. I painted it black to suit…Done!
With a drum mag of glow gels it makes for a great back up blaster for night