Sorry, I don't know to what extent "home-made" animals were sold commercially, but I would be surprised if there weren't a lot. Your posting reminded me - their proper job title was, I think, Scientific Glassblowers. The top men shared highest-earners place in the factory with the top big-shop blowers (i.e. working at furnace type blowing, making up to 200 litreflasks).
I have a vague recollection that a couple of the lampworkers (let's stick to the common term) had left to set up their own business. I don't know how much of that was animals etc and how much jobbing scientific work for small labs. It must have been lucrative to have quit their original, highly paid jobs.
For the record, all of this would have been in the Sunderland area.