I have read on this forum somewhere the bolt with a hole really isn't necessary, maybe someone could chime in. I pulled my engine apart, it did not have the bolt with a hole.
If you have the dripper for the chain you don't need the drilled bolt.
No dripper, need the bolt.
You can use the cam plug as stated above, or you can drill a bolt for it.
Personally I like the bolt or the drilled plug due to it's ability to oil the chain real well.