I has been a nightmare to find 1:400 GSE accessories for my model airport.
Only Gemini Jets and Witty Wings have some at this scale at a reasonable price, but their style is old and are becoming an antique.
Other brands like Dragon wings have some more modern sets, but extremely hard to find, and if you do, their prices are insane.
Perhaps there is a previous post regarding this topic, but I am sure this may helps others.
So, I spent a lot of time surfing on the web and found 2 online stores that seem to be very interesting, not cheap though. One is located in the UK, the other one in Australia:
Ornamental Castings - Ground Service Equipment
I just placed an order of some stuff, will see how it works.
They are an alternative, so I hope this helps someone to get some 1:400 GSE accessories.