I wouldn't sweat it. There are dozens of places on the internet that you can find printable sight in targets that have a 1" grid on them for scope adjustments. Also, keep in mind that the purpose of the boresighter is NOT to sight in the gun. The purpose is just to get your first shots on paper so you don't waster a bunch of ammo just trying to hit the target, nothing more. They will not substitute for zeroing the rifle by shooting groups. So what I'd do if just print out some sight in targets. I like the ones with the "X" shaped crosshair alignment arrows, preferably in a high-contrast color like red or orange so you can see the bull easily. Set the target out at 25 yards if the velocity is less than 2500 fps, and at 30 yards is 2500-3000fps, and 35 yards if 3000fps+. Put the boresighter on the muzzle (or in the chamber as appropriate for your particular model) and set the rifle on a very steady rest. Now adjust the rifle until the laser spot is on the target. Then, looking through the scope, adjust the crosshairs until they are coincident with the laser spot. REMOVE THE BORESIGHTER! (see image below)
Now, load the rifle and carefully fire a round aiming at the bull. The Point-Of-Impact (POI) should be pretty darn close to the point-of-aim (POA), but it will almost certainly be on the paper unless you did some drastically wrong, or the boresighter is defective. Adjust the scope to bring the POI to the POA and fire again. Now you should be dead on or within 1/2" (close enough). Move your target out to 100 yards, and shoot a group. Adjust your zero as necessary and then you can move the target out further for longer zero ranges.
I do exactly as described above, but I just take out the bolt and use one of the most sophisticated optical instruments in God's creation, my eye. I just sight through the bore to the target, and then without disturbing the rifle I adjust the crosshairs so they match. I'm usually within 2" at 30 yards, which is good enough, and it's free.
Mike