Citroen Xsara external door handle broke

If you have access to the inside of the Door I would expect by removing the Door Card that you would gain access to the handle from the inside. Access will be tight at best. It is not clear from the query whether the Handle has just come undone and could be re-instated or is physically broken and needs to be replaced. If it is the latter I expect you could get a replacement in a Scrapyard.