One suggestion that comes to mind is to try to come up with the closest substitute word you can think of and memorize that word. You can try to recall it later in order to figure out what the missing word should have been.
For example, if I was having a conversation about selling real estate and was having trouble thinking of a word that means “the percentage agents get paid when they sell a house”, I might either commit the word “percentage” to memory—or, say I mistakenly coming up with the word “gratuity“. As long as I know it is wrong, I could memorize that word by, say, mentally placing it in a locus nearby. Either way, later on I would retrieve the word that I memorized.
Presumably, it would be enough to remind me of the conversation and, hopefully, that word would provide enough clues to figure out the word I really wanted.