@Julian Any chance you've got more than just Meraki cameras on your networks? If so, you can script the creation of traffic shaping rules on Meraki MX on a per-IP basis if creating a separate vlan is really not going to happen. Just make sure you set DHCP reservations for the cameras.
If you're using AD DHCP for the cameras, then you can use PowerShell to build out a script to filter current leases for the active camera mac addresses, then create DHCP reservations for them.
I really would prefer a separate camera vlan, but I know how tiny offices go.