There is only 4 or 5 breweries that can legally produce the Belgian (Trappist) ales you refer too.
I believe I've seen an abbey brewed ale produced here in WA that is sold as "Trappist ale." Whether it is an "offical Trappist ale" or not, I don't know. I've heard it's good though!
The secret of Belgian ales is the yeasts used and the tanks it made in. Belgians breweries are usually never cleaned and use open shuttered aging rooms that allow a wide variety of local yeasts to float and settle in the tanks. This coupled with the concrete tanks imparts a unique flavour profile. Rich, fruity with a uniques nose. Not drinkable to everyone. I am a long time beer fan and can usually only appreciate Belgians- Chimay, Trappists, Abbeys, Dubbels, etc.- with food as in a hearty meal. I cannot just sit and drink them on their own. But thats me.