Get Your Dog Care Questions Answered by Experts
You may find this site interesting reading
You might want to read here about Pen-G
I'm not seeing combiotic in catalots like this one
So maybe Pfizer renamed it or is not making it anymore. I do see it for sale from China but only in high volume.
Hope this helps you!
I saw one in china
and one in India
and a foreign ebay item
Here the manufacturer was Pfizer and you could write them about it