Wild collected ladybugs are unsustainable, bad for the environment and not the aphid predators you hope they would be. Find out why, and discover the alternatives to ladybugs that commercial growers use. Wherever you buy ladybugs ask them to provide you with lab-reared alternatives - ones that will destroy your aphids and only contribute positively to your environment.

Source: https://biocontrol.entomology.cornell...

Instead of buying ladybugs, try Aphidoletes aphidimyza the Aphid Eliminator.
In Canada you can get them here: www.thebuglady.ca
In the US you can get them here: www.evergreengrowersupply.com