Engineering wise...
Durability is in the socket not in the plug.
I know you don't want to hear this but it's a fact. Loose, annealed prongs and wipers in the socket receptacle cause a loose fit and the "finest quality" plug will be helpless against it.
This is what I did - which seems to help more than all the other jury-rigging attempts I have ever done...
Clean off the brass prongs on the plug - new or old.
Get electronics solder 60/40 or better yet 63/37
A good minimum 60 watt soldering iron.
A jar of paste flux from Home Despot
Using care to not damage the plug body, tin all the brass connectors sticking out the plug. Tin them not overlay them with thick globs of solder. When in doubt, strike the fresh hot solder to knock excess solder loose.
I am not exactly sure why this fix works so well. The added thickness the solder makes surely must not be enough to make the fit that much tighter.
But, oh well, it works and maybe that's the whole point.