Nematodes (microscopic worms) are for controlling vine weevil larvae.

Aphidoletes Pupae help control aphids. Leave them under an upturned pot to hatch and after couple of days small flies emerge. The orange larvae are voracious predators of aphids and will kill and eat their prey until fully gornw and ready to pupate.

If you plan to use biological control then you must not be using any persistent pesticides. Also you have to introduce the bio-control after the pests are present; also with bio-control you can reduce but not be able to eliminate pests completely.

Ordering has to be mail order mostly.

Reference: American horticultural society. New Encyclopedia of gardening techniques

You don't need chemicals for aphids. If you see them on a plant, just blast them with the hose. Do this once a day and they should diminish. You could also mix up a spray bottle with diswashing soap and water and spray them. Or just wipe them off with your hands. That's what I do. Ladybug larva do eat aphids, but I'm not sure importing lady bugs is worth it for aphids.