Broken plastic guide on tubes - how to tell which way the tube fits in socket?

ozzy, that would work if there were other tubes to check but in this set up, it's the 6SL7 that is broken, along with both my 6SN7>6F8G tube converters that I'd like to not replace.

imhififan, thanks, that's a great replacement piece. Not sure how I would know which direction to install it however.
arion, yes, the pin is completely gone.

imhififan, I do and will give that a try. Thanks!