As far as I know the bears are still available in crafting, but as
@FieryArien says, it is a risk because you never know when something might be removed from the crafting rotation. Ordinarily I would say it is a risk worth taking because these types of buildings would come around very frequently. However, with the changes to the way the MA gives crafting recipes I am no longer sure how long you may have to wait for them to appear.
I'm inclined to agree with
@Julian. You might as well hold onto the one you have because it's only really the feeding effect that you're looking for, which doesn't change chapter to chapter. You will probably want to be holding at least 3 bear artefacts before even building it as I'm not sure it's worth the pet food for a very small troop production increase.
We will get another bear in the Autumn event, but it isn't going to be a replacement for the Brown Bear. The hope, on your part, is that they offer an artefact conversion recipe like they did with the Phoenix event, or that they offer a few 2019 artefacts.