Where to buy smart on/off in wall switches?

Welcome! :sunglasses:

Some manufacturers are readying Z wave plus models, so you may see some short stock for the older zwave classic models. But in general you should be able to find things.

See the following FAQ for a list of vendors (this is a clickable link)

And this thread should also be of interest. The light switch discussion starts about 30 posts in.

Nortek is one of the largest manufacturers of Z wave devices in the US. They sell under many different brand names. “Linear” is the brand sold to contractors. The exact same devices are sold at retail under the GoControl brand, and may be easier to find that way.