There are a few third party remote controls, but all require an extra box to do the integration. The ones I use are…
@DrCWO has a few devices, although RooMax is probably the best (I have one and am really enjoying it).
You need a raspberry Pi with his software or a rooMax box, and a paid license (as well as buying the remote).
I use a few IKEA remotes. To use these you need a raspberry pi running home assistant, with a zigbee usb dongle. The software is all free and open source, but you need to set it up.
The other option that comes to mind is. Raspberry Pi running rooPieee - which can work with a remote control.
This slightly out of date guide is easy to follow and gives you the basics.
I use rooPieee to give me Roon endpoints (which you don’t need), but it can also act as a remote for any zone. I don’t have personal experience of the remote facility.