You seem to be experiencing jealousy stemming from envy about S's luck in finding dating partners. You'd like to find some dating partners too, but so far it's not working.
Some things you could try are:
In addition you can google "polyamory" with the name of your city or state and see what turns up.
"As for where to meet poly people, if by some chance you are interested in anything alternative like Renaissance fairs, goth culture, sci-fi conventions, indie music, bdsm, or any small fringe group, you will be more likely to meet people who have at least heard of poly and are accepting of it."
-- SpaceHippieGeek, http://polyamoryonline.org/smf/index...57394#msg57394
Even if it's not an "alternative" type group, if there's a club or something in your area that does something you're interested in, you can always join that group and it just gives you a way to get out there and meet people. If you meet someone on a platonic level and get to talking about poly, then they can decide how they feel about it without any "pressure to agree." Then if they do decide poly doesn't bother them too much, and some kind of romantic connection subsequently develops, you'll already have "had the poly conversation" with them.
Women often have better luck at finding dating partners than men, so you will need to exercise some patience. Focus on your own search and don't be too distracted by your wife's good luck.
Sorry there's no easy answers.
Try some of the above resources, and see if it helps.