Which distributions maintain a kernel package with grsecurity support

NetSecL is a OpenSUSE based distribution which supports grsecurity by default.

From the homepage:

NetSecL is a hardened,live and installable OS based on OpenSuse suitable for Desktop/Server and Penetration testing. Once installed you can fully enjoy the features of GrSecurity hardened kernel and penetration tools OR use the penetration tools directly from your live DVD. GrSecurity is a great security enhancement that you can enjoy with NetSecL and have a normally functional OS together with the NetSecL Firewall and Penetration tools you are always ready and know at what level your security is.

Pentoo is a gentoo based distribution which includes grsecurity by default, from the wikipedia page:

The Pentoo kernel includes grsecurity and PAX hardening and extra patches - with binaries compiled from a hardened toolchain with the latest nightly versions of some tools available.

Alpine Linux uses a kernel with grsec by default so once installed updates require no added effort. Though my understanding is they use an unsupported grsec kernel.

ArchLinux have newest kernel with grsec in their repo. More info about this package can be found on it's dedicated wiki page.