Like Underpants says, tiger worms are quite simple to set up and continue to to good numbers/product. But tiger worms will die very quickly if using in salt water. I was desperate once and purchased tiger worms from a store to use in salt water - never again ... expensive and were dead quickly.
I wont buy tube/beach worms at all, just far too expensive for a couple of them. Best to practice, practice and practice sourcing your own from the beaches.
Even seaweed worms are easy to get, just find very old seaweed sitting high on the sands and start scrounging through the weed to fin