If the soil has sufficient organic matter worms will come naturally. If there isn't enough food for them, importing them won't help. They'll leave for greener pastures ... if the moles don't get them first.

Your could try worm grunting and get buckets full for free.

Out of curiosity I kinda want to give it a try some day.

Maybe try putting in a couple worm towers and growing your own stock? You might just be growing mole food once you empty the towers back out into your gardens, lol.