I haven't look for this extension, but if it's like I think, you will have a hard job to make it work.
I have tried with some xul help system from Nvu/Kompozer, Seamonkey, xpcomviewer and I never can make it work. I think that some services are missing. Our cleaning in mozilla is good to make K-Meleon thinner, but it don't allows some features. With a version, I made it work partially, but not as it ought to do.
So I haven't continue it.
Good luck ...
Mozilla/5.0 (x11; U; Linux x86_64; fr-FR; rv:38.0) Gecko/20100101 Ubuntu/12.04 K-Meleon/76.0
Mail : alain [dot] aupeix [at] wanadoo [dot] fr
Ubuntu 12.04 - Gramps 3.4.9 - Harbour 3.2.0 - Hwgui 2.20-3 - K-Meleon 76.0 rc