Hello & welcome, I am Dr. B, a licensed veterinarian and I would like to help you with your wee one today.
Now there are some equivalent products that we do use in kitties with this type of situation. In regards ***** ***** dietary fiber (which is what the psyllium husk that was in the Feline Comfort product is), we will use products like Protexin Pro-Fiber (More Info). This product is quite a good one for supplementing fiber and it also contains probiotics (ie EU-registered probiotic Enterococcus faecium (NCIMB 10415) E1707 to restore normal GI microflora) and Preplex prebiotics (ie fructo-oligosaccharide (FOS), acacia (Gum arabic)).
Alternatively, a good probiotic dietary supplement that we do often use in cats is Fortiflora (More Info) and this can be used in combination with an OTC fiber supplement (ie a 1/4 tsp of Benefiber).
In regards ***** ***** the Luxolite, we tend to use Kaolin (another clay product) to slow loose stools and naturally absorb excess GI fluid. This can be purchased OTC at the chemist and used as on its own. Or you can use it in combination with a pre/pro-biotic supplement like Protexin Prokolin (More Info) or Canigest (More Info).
Finally, if you suspect she has GI gut inflammation or ache as part of her condition, then the slippery elm (a precursor to aspirin) in her previous treatment may have been of benefit for her. And while not present in most GI products here, I would note that Dorwest Veterinary Herbals, do make a product that could cover that side for her as well (More Info).
Overall, there is no exact product that matches what she has had before. Still we can combine the above products such as to meet her requirements and settle her loose stools for her. Therefore, I would advise trying some of the above to try with her. Perhaps you may want to consider just starting with the Protexin Prokolin (since it available OTC and has the clay, probiotics, and is a treatment of choice for loose stools in kitties here) on its own to see if this one treatment can soothe all her signs alone. If it can, then may just streamline your supportive care for her.
Please take care,