Well, you will have to create a link (a transit VLAN)between this hub and the router you have on your network.
That's why I asked for a topology to understand how your network is logically.
Having this link, simply create a static route to 198.19.x.x pointing to 192.168.0.243 as the next hop.
It's a pretty basic routing to be honest.
I am not a Cisco Meraki employee. My suggestions are based on documentation of Meraki best practices and day-to-day experience.
Please, if this post was useful, leave your kudos and mark it as solved.