I agree with trying the different apps (Grindr, Scruff, Growler). Get a new account on them, put in the profile that you are a couple looking for another couple.
My ex and I used to look for others to play. We had plenty of 3ways and 4(or more)ways, but the best was when we played with other couples. So more relaxed and fun. We had a screenname on gay.com and aol (those were the popular sites at the time) that advertised we were a couple looking for other couples. We found quite a few that were interested in other couples. We became really close to 2 of those couples. We would go out to dinner, movies, bars quite a bit and then have great sex later.