You may have seen ads for companies that do searches for a flat rate, or been approached by or run across people offering to do certain search tasks for you for a fee. Ask a lot of questions. There are places that swear they will cheerfully continue searching if they give you the wrong match. On that premise, they could tell you they are searching forever and you get nada. Ask what happens if you find while they are still looking.
Some companies offer a search for a flat rate.
If you already have gotten a name or other critical info, you should be able to bargain a searcher down a bit since you are coming to them with a lot of info already. If you wonder about a place or person, post it and let's see if anyone tried it or has a good or bad experience to report. I will gladly post it elsewhere and see if I get any response to your query. Some is good, some not. Again seek opinions, check with the BBB in the home city.