Hi,
Yep, we can buy lady bugs. Mind you it wasn't my idea.

I think our neighbor is an active aviary so I'm certain the bugs didn't make it. However, the bugs in the greenhouse cleared up the aphid problem in a few days.
So, a handful of ladybird bugs in a greenhouse is a good idea.
*Update*
We found the small worms on the back side of the broccoli leaves. We used the old fashioned method of collecting them and squishing them. We counted nearly 100. We did locate where they hatched. Got to figure out a better way of catching these before they become a problem. A few worms tried 'bungi jumping' to get away be we caught em.
We're experimenting with beer now on the slugs.
Beneficial nematodes have been added to the soil in our garden.
Regards,
Chuck