I will add to the already great responses you've received.
Gouramis can be extremely difficult to gauge (in terms of behavior). I like to look at them based on the genus, because I've found that to be my most accurate table of prediction.
The Trichogasters (Opaline, Pearl, Blue, etc) do not tend to do well together. I've heard of successful, long pairings, but have never had one myself--regardless of the ratio of male/female or combination of other tank inhabitants. I've also found (contrary to most information you'll read) the Pearl to be nearly as aggressive as the Blue and Golds. Therefore, I'd recommend one (single) male per tank. Since you're working with rather large space in your 75, you might have better luck, but I'd be prepared to remove one if necessary.
The Colisas are a little better suited for pairings (male/female). Most of these guys don't create too much of a fuss if there's another "fella'" somewhere in the tank--but I've also had a voraciously nasty Honey Gourami situation once (two males with multiple females). The Indian Banded (aka: "Giant") or the Thick-lipped are almost sure bets. They're also rather docile, for the most part. I'd be more inclined to recommend these two species for multiple males in the same tank, but again proceed with caution.
As for why you aren't locating females, that's a problem I've noticed myself in the past couple years. The stores have difficulty selling the females because they're usually so drab looking. The males are show-offs and have that brilliant color, one of the main reasons for keeping the Gouramis, so it's supply/demand there.
If you're truly interested in putting a pair in, I would try my hand at the Indian banded. There are some available from
www.franksaquarium.com.
I believe he has both males and females in stock and I'd just request a pair and try that. The shipping can be expensive, but you're also getting exactly what you want, with a much greater potential for success than just obtaining two males out of default.
Anyhow, good luck to you and let us know what you decide on.
K. Blane