Stretched chain and long miles?

[Gnasher]

As a last resort and ONLY if it's got a very limited life until you are going to change it, plus I'm assuming you are awaiting parts which is why you cant change it plus you have the tools to do the job?

I've done this for a few customers in the past.

Split the chain and remove a link, refit using a NEW soft link it will easily last 500 miles.