Repeaterbook does list GMRS repeaters.

Only GMRS repeater owners or their designees are permitted to add a GMRS repeater to Repeaterbook. No person should gather data and add a repeater to this site without the permission of the owner of that repeater. A violation of this policy could result in the dismissal of membership rights to Repeaterbook.com

You must have a valid GMRS or Amateur Radio callsign and be logged in to add a GMRS repeater. The system will perform a check against the Federal Communications Commission (FCC) database before allowing you to add the repeater to the database.

When the repeater is added, the call sign of the person who added the repeater is recorded and is allowed to edit the repeater. This means, if you hold both a GMRS license and an Amateur Radio license, you can add the repeater when logged in with your Amateur Radio license callsign. If the repeater holds your GMRS license and you added the repeater when logged in with your Amateur Radio license, you will be able to edit the repeater when logged in under either call sign.

You must have a valid GMRS callsign and be logged in with your GMRS callsign to edit a GMRS repeater. The callsign must be the same as the person who added the repeater or that of the repeater call sign.

When the repeater is added, the call sign of the person who added the repeater is recorded and is allowed to edit the repeater. This means, if you hold both a GMRS license and an Amateur Radio license, you can add the repeater when logged in with your Amateur Radio license callsign. If the repeater holds your GMRS license and you added the repeater when logged in with your Amateur Radio license, you will be able to edit the repeater when logged in under either call sign.

If a repeater is entered with incorrect information that would invalidate the listing, such as a callsign that does not belong to the repeater or is not a valid call sign, the repeater may be deleted from the database without prior warning or notice.