Answer: This is a gorgeous plant but it is single, here is the catalog description:
Beautiful, heavily fragrant reddish-purple to dark purple single blooms come late spring, extending the lilac season! An outstanding open branched, upright habit useful in mixed shrub borders or in mass plantings with other lilacs. Deciduous. Full sun. Moderate grower to 6 to 10 feet tall, 6 to 8 feet wide.
There are hundreds (maybe thousands) of cultivars of Syringa vulgaris or common lilac. For the most part S. vulgaris are considered hardy to zone 3, and your zip code places you in zone 4 so hardiness should not be a problem. Yankee Doodle, Frank Klager and Monge (more of a dark purple red maybe) for instance are a very dark purple, but single as is the Ludwig Spaeth. Vulcan is another good purple but also single. President Poincare has double purple flowers but is maybe not as deeply colored. Adelaide Dunbar might be a good choice, it also has some mildew resistance which is nice.... to some extent the evaluations of color and fragrance are personal, and there are some trade-offs, so one person's "best" will not necessarily be the next person's top choice. If possible it is probably best to see it in person to make sure it is what you have in mind. On the other hand I have never seen a "bad" named variety lilac.
If your local nurseries (here is a zip code based dealer locator to help with contact information)
do not have a wide selection (selection is usually best just prior to the lilac bloom season) you may want to look into mail order from specialty nurseries such as
Fox Hill Lilac Nursery
I hope this helps!
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