We are looking to book the night train from Paris Austerlitz to Cerbere in April. I know the schedule isn’t released yet and I don’t think you can make bookings, so I’m testing the booking system out for earlier dates in February.

So I’m looking at 09 Feb, 20:08, arriving about 10am next day, direct train, for 2 adults and 1 child (2 years old). 

Using SNCF or Traline I can see that private couchettes are possible for that route, but obviously I don’t want to book on there, I want to book through Eurrail.  

When I try and make a seat reservation with Eurail, there is no option for a private cabin upgrade, and also on SNCB there is no option for an upgrade. 

Does anyone know if there is any option on any website to make an Eurrail booking with private couchette, or do I have to persist with SNCF over the phone?