Hi Chris,
The cleaning hose you have is the best starting point.
The rest of the advice I gave for a machine that has already developed urine odour after cleaning care home was:
After such a job I always sterilise equipment. Any hand tools are dropped into a bucket of steriliser for a while, the exterior of the wand used is sprayed with the same. Then with vacuums running I spray Urine neutralise into the end of vacuum hoses.
I then switch off for a few minutes, re-attach the wand and suck the steriliser from the bucket. After re-draining the tank more urine neutraliser is sprayed/sucked into the solution hoses before putting them away.
I find that this keeps all the equipment odour free.
For now I would suggest that you at least perform the last stage of this and possibly put a gallon of very hot water in the waste tank, add chlorine bleach, switch on for a few seconds to draw the chlorine gas into the vac units, then leave overnight with closed tank.
For on-going maintenance, get a male connector and screw in a jet or even a hose-tail. this can be plugged into your solution line and used to flush out the tank (drain open) at the end of each job.
Then a quick spray with a bactericidal odour neutraliser around the tank and leave the lid open so that the tank can dry and further inhibit the growth of bacteria.
John.