TM7
Try an "O" Ring chain if you haven't done so already. This chain has the rubber "o" rings on every link with the rollers being packed with grease.
You will find an incredible difference in the amount of times that you won't have to tighten the chain as well as the total life of it as compared to a standard chain.
This chain will still need to be lubed like you regularly do and some of those aerosols like (Chain Wax) work great while being formulated to condition and protect those "o" rings.
If your chain is currently catching or popping, or if you can pull the chain more than 1/2 the tooth lenght at the 3 O'clock position on the rear sprocket while facing the sprocket,
You will need to replace both front & rear sprockets as they will quickly ruin the new chain if you don't.