Just go to your local fishing shop and get some red wrigglers and make yer own, best part is your waste is their food, cost zero to maintain just the ends off yet veggies, I don't collect the castings but once a year and mix it into my next years grow. What I do is pour water through it and collect it and water the plants with that and some seaweed between feeds. So it kinda goes pure water, then worm juice and seasol then a feed with nitrogen and guano and maybe a clean water flush in between if the plants are getting too many nutes, they kinda tell me when I'm pushing too hard so I'll ease off and just water.
I would so like to have my own worm box. Years ago I knew this old man who had a Redworm box and I used to get worms from him for fishing. It was Loaded, it smelled so good.