You can get steering "stabilizers" ("stabilisers" often wont show them in a search) online if you want to pay for a more basic one than the bullit one but idk if they'd work with that tube size/shape. I think they're intended more for dutch bikes more than cargo bikes.
Thanks. I can see the options on that site, look like a good prefab solution, near identical to what I’d try to put together anyway. Will have a proper look this week.
You can get steering "stabilizers" ("stabilisers" often wont show them in a search) online if you want to pay for a more basic one than the bullit one but idk if they'd work with that tube size/shape. I think they're intended more for dutch bikes more than cargo bikes.
hollandbikeshop.com have a few