You need to contact the cruiseline of your choice direct. Contact addresses are easily found on cruiseline websites..........I don't wish to add to your problems, but have you enquired about insurance? That cost alone could be a deal breaker............Wilba.
You need to contact a good agent (try the free Phone number at the top of this page) or contact the cruise line directly .
My Nephew needs oxygen on occasion but took his own supply ,I have seen people with an oxygen trolley and would presume they supplied there own .
The ships do carry oxygen for emergencies but I would not think they would supply a free to use supply ask the question and hope it works out well for you both...Taffy.
My employer has portable oxygen machines that are light and portable. But i dont know anything about this side of the business i'm afraid. This link may help you - http://www.bochomeoxygen.co.uk/images/PDFS/J12-3244%20406745_Healthcare_XP02_Concentrator_p1-12.pdf
They have a helpline 0800 136 603 and they will tell you more.
This link has more info . http://www.portableoxygen.co.uk/?gclid=CLmA166up7YCFePHtAodR1YAtQ.
Assume your OH uses a concentrator? Could you perhaps look into hiring one at Southampton, if that's where you leave from?? I needed oxygen on one P&O cruise and had to use a concentrator for a few days so they obviously have them onboard for emergency use.