Cradlepoint makes very good enterprise-grade cellular modems with wired Ethernet support. They're expensive and I'm not sure if individuals in the US can buy them without going through a grey market vendor. For some reason or other, the cellular industry doesn't like it when devices are readily available to end users.

It's also possible to use some home routers 'in reverse,' to bridge a wifi signal to wired ethernet. Devices on the wired segment will be stuck in a double-NAT situation, however.