R9237-9079 Square couplers

Thanks chrisjo but the reason I didn't direct link is because it gives an error if you haven't already entered the site from this link:
https://store.mattel.com/transition.aspx...&sec=10796

Here's the image with most of the white cropped out (which doesn't show the hole size, should have posted this earlier):

They're the coupler type used on Harvey's coach and motorized tenders.
If no one has an answer I'll probably just buy a couple sets anyway and find out for myself.