Samsung has decided to get out of the business of supporting and selling home automation hardware. So they are turning that over to partner companies. So far the only one that has been announced is Aeotec, which is taking over the devices for the EU and for the US. Smartthings will continue to provide the app and the cloud.
The first models from the new Aeotec line will be identical to the existing smartthings devices, just with a different brand logo.
That will include the button.
However, they let the supplies of the old logo devices sell out before Aeotec was ready with the new logo devices, so it may be a few months before you can buy one.
Here’s the official announcement:
An Update Regarding our Hardware
And as @psbarrett mentioned, if you don’t want to wait, the IKEA “dimmer“ is a simple inexpensive Zigbee button which is a good substitute if you don’t want to wait as long as you are OK with just an on/off function. 