Ethernet switch with 8 ports and PTP
Ethernet switch ASICs broadly fall into two categories:  Small, low port-count unmanaged switches with rudimentary features, and big, high port count, highly sophisticated managed switches.  There is not much in the middle--or at least not much that is accessible in low volumes.  If you are looking to build this device in large enough quantities any of the major networking manufacturers will be happy to provide you with advice or samples.  Different manufacturers will have different ideas of what "large enough quantities" means.

If this is a low quantity project, you have a few options here, based on what I've seen when looking for off-the-shelf switch ICs for my own projects:


Use the KSZ8999 or a similar non-PTP switch, attach a microcontroller to its MII interface, and implement PTP on the microcontroller.  Many MCUs with built-in Ethernet MACs can do hardware timestamping which should be helpful in implementing PTP.  I'm not sufficiently familiar with PTP to know if implementing it this way versus directly in the switch presents any substantial downside; I imagine it depends on your required precision.
Use two or more lower port-count PTP-enabled switches, and connect them together.  For instance, if you can find a switch with four PHYs plus an MII, you can usually connect two of these back-to-back via the MII.  In networking terms, it's still two switches, but they can be neatly packaged into a single box.  This will probably require that each switch IC have its own MAC address.
Use a single, more sophisticated managed switch.  Many of these sophisticated parts have dedicated processors built-in to facilitate complex control of the switching engine, but you can also program them to do whatever you want.  The upside is flexibility--you can implement any features you want.  The downside is you have to write the software, although the manufacturer will probably have some resources to help you get started there.  The other downside is that this category of part can be challenging in terms of hardware as well--it's not uncommon for high performance parts to require external DDR3, or expose most of their ports via QSGMII, for instance.