Want mugwort but not sure where to get it in the UK

I'm going around the UK for the next month, mainly staying in Scotland and England though, and wanted to buy some mugwort. Buy because I honestly don't trust myself to forage it, and thought it'd be nice to support local businesses! Although if anyone has tips on foraging, I'd love to hear as well.

If anyone has any recommendations for places to buy some, it'd be much appreciated!