There are a variety of direct plug-in filters that can supplant the PCV valve. One popular and easy to fit unit is from K&N: K&N Crankcase Vent Filter



I don't know the grommet ID offhand, but you'd just need to order the appropriate flange diameter and simply replace the PCV. You can then either put a plug in the PCV draw-off hose or one in place of it where it mounts.