To be clear, are you looking for something that actually controls the circuit branch, that is, that gets wired into the Mains and replaces a regular switch ?
Or are you looking for something which is battery operated and communicate to the smartthings hub which then passes the message along to either smart bulbs or other smart switches on your system?
And you are in the US, correct?
There should be quite a few options, but it will depend on the answers to these questions.
Meanwhile, take a look at the buttons and remote FAQ. It has some devices of all of these types.
( The topic title is a clickable link)
Most of the posts will include a link to a discussion thread on that particular device. Please take any follow on questions about specific devices to those threads, and don’t post them in the FAQ. ( or, of course, come back and ask them here.) The FAQ is just supposed to be one or two posts per device so it’s easy to read through later. Thanks!