Just buy a normal small rachet,a hex bit set and a 15mm socket. I would just buy a Bacho small rachet set and use it for the house / DIY / bike
I was not looking for alternatives.
Finding small ratchets is easy enough, there are all over eBay and Ali and they are cheap. I already have a couple, including the one in the original Brompton toolkit.
But I like the idea of the ratchet insert for a 15mm spanner and if they were available separately, at reasonable cost, I would get one. But I aint going to pay £75 for a Brompton tool kit to get one.