ThanksYou cant have looked very hard, there are quite a few, maybe not your exact model. Here's a 2020 'new' 6 speed still in box which should give you an idea.
https://www.ebay.co.uk/itm/133548952091
Bromptons hold their price very well and new are hard to get hold of right now so you can pretty much name your own price or whatever you consider fair.