I carry my bike in my VW T5 van using a fork mount fixed to a steel bar on the floor of the van. The 9mm skewer size is easy to get made by a company called Delta but I could not source a 15mm bolt through version anywhere in the UK. I made my own in the end....that is 15mmx100mm. Now with my e bike I have boost hubs so need 15mmx110.....again no one in the UK sells them. So I am going to have to fabricate one again....BUT....I have found a ready made part that gets most of the job done. Pendle do a roof rack bike carrier using a fork mount and sell separately as spares the fork adapter part in all hub sizes.