Humber Nurseries on Hwy 50 @ Hwy 27 has them.

www.gardencentre.com

They are dioecious (male or female) so you will need at least one of each gender. If the gender isn't specified, you will have to play the odds with 3 or 4, eventually removing/replacing the extra male shrubs.

I went there physically last weekend and they had 3 plants of unknown gender. They where larger plants from the previous season and the tags had being washed off - hence not knowing their gender. I decided, not to risk it as the chances are they left over males (most often the case since you need less males). If you have seen new stock, I will run back....

Sheridan nurseries (call to find out which location has it)?
How about Connon nurseries in Waterdown?

I get the impression that Sea Buckthorn is commonly offered with the gender unknown. I think it might be because it's typically grown from seed and used in naturalized mass plantings where a few guys in the mix is not a big problem.

If it's flowering, one can usually identify male from female....look for the presence or absence of the pollen bearing stamens.

Sea Buckthorn is what I got. Two varieties of females and one male. They spread all over. The male has grown tall and shading everything. The females are even worse. I have seen them sold in Stafford during Garlic Festival, which is sometimes in late August or early September. I bought mine 10 or 11 years ago from a nonexistent nursery. If you want to block an area females are better for that. You can grow them without a male, except there wouldn't be any fruit. The ones I grow are no more than 6 ft. and thorny.

Thank you Yugoslava. They happy in the ground and I look forward to my first crop! Much Much appreciated. PS love your garden!

It was nice meeting you too. Glad you like the garden.