Collimating at f/8 is very non critical compared to f/4, A simple site tube as Aurora details is about as precise as you need be. Heck at f/8 I often just eyeball it by centering my eye as well as possible in the draw tube at the image plane. You have lots of leeway at f/8 without it botherng the image much at all. For my f/5 I do use Orion's combination cross hair sight tube (I wish it was double cross hair)/Cheshire "eyepiece". The Cheshire part is helpful for collimating at night as you can use your map light to illuminate what you are doing by shining it onto the 45 degree matte face. I then finish up with star alignment for the final tweak of the f/5. I've never found a star alignment needed with the f/8, it was already close enough.

As explained in the last link Dave gives, and maybe others I've not looked, the laser collimator isn't nearly as useful as many think and can, in fact, lead to a really lousy collimation job. I've seen it happen many times. It's a great way to go wrong with confidence! Correctly done, a barlowed laser is more useful but totally unneeded at f/8 as far as I'm concerned. A simple site tube like Aurora details does the job just fine. Especially if you only need to align in daylight.

Rick