Double Threat is available to order through most major booksellers in North America, including Amazon.ca, Indigo.ca, and in the US, through Target.com, and Amazon.com.
It is also available to buy in Chapters stores across Canada.
(See below for independent bookseller locations.)

Libraries and wholesale or institutional orders: 
UTP Distribution
5201 Dufferin Street
Toronto ON Canada M3H 5T8
Tel: 416-667-7791 or 1-800-565-9523
Fax: 416-667-7832 or 1-800-221-9985
utpbooks@utpress.utoronto.ca

or

Ampersand Inc. Email: Morgen Young, Vice President.
Suite #213-321 Carlaw Avenue, Toronto, ON, M4M 2S1
T 416 703 0666, toll-free 1 866 736 5620.

Double Threat is available at many independent bookstores, including:

In Toronto,  both Israel’s Judaica stores:  in Thornhill (441 Clark Avenue West, in the Kosher Sobey’s mall) and the 1172 Eglinton Avenue West store (west of Bathurst).  At Squibb’s Stationers, on Weston Road.

In Montreal: at Bonder Books on Westminster, and Bibliophile, on Queen Mary.

In Burlington, Ontario: at A Different Drummer bookstore on Locust.

In Port Hope, Ontario: at Furby House bookstore.

In Halifax, at Bookmark on 5686 Spring Garden Road.

In Charlottetown, at Bookmark 172 Queen.

In Victoria at Munro’s Books, 1108 Government Street.

In Calgary at Owl’s Nest Books, in the Britannia Shopping Plaza.

In Edmonton, at Audreys Books, on Jasper Avenue.

In Kingston, at Novel Idea at 156 Princess Street.

In Ottawa, at the Perfect Books store, and Gateway newsstands in the Bayshore Shopping Centre, and the St. Laurent Shopping Centre.

In France, at the Juno Beach Museum gift shop in Courseulles-sur-Mer!

In Australia.