Is there a product for adding betta to a community tank within a container?

Yes. Some pet stores use breeding nets/tanks to keep the fish in the bigger tanks for more space.

they can be small, but there are different options. There are suction cups, but if this is a long term thing, then I wouldn't recommend them. There are nets that hook to the side of the tank and some that are free floating. I would suggest one that hooks to the side.

Now there are two types of breeding nets:

Nets (mesh walls)

and

Plastic

The net breeder I have has mesh walls with artificial plants that hook to the sides.

The other types are plastic ones, which more people recommend. These cages have air holes for water to come in, and rounded edges for safety issues. You can purchase a 'double' breeding net, which has more space. I would ask your local pet store for assistance.

Just make sure that the Betta can reach the water level for air and to build a bubble nest.

I hope I helped!

You could use one of those "breeding traps" that you put guppies in, transparent plastic with the grate at the bottom.

They are small, but the betta has the same clean filtered water as the reast of the tank, so it's not like it's a 1/2 gal tank of cruddy water. Throw some small plants in there and he should be OK.

I wouldn't trust suction cups, they eventually come off and the betta might escape. Get one that physically hangs on the side of the tank.

Ian