Cannabis might help.
In a 2004 open-label pilot study conducted on patients with advanced multiple sclerosis, researchers concluded that a 1CBD:1THC (2.5mgs of each) spray, and a 100% THC spray (2.5mg of THC) "significantly reduced urinary urgency, the number and volume of incontinence episodes, frequency and bed-wetting."
While the pathophysiological causes of incontinence in MS patients differ from those without, they do share some similarities.
I would recommend 1:1 products, such as
https://www.hellomd.com/products/58ed567a63d9e91a57368cc6/11-sublingual-drops – 7 drops would contain approximately 2.5mg
I hope this helps!