I finally purchased a back pack for Rex, this week while we were in windsor. But here's the thing, he doesn't have a collar, all his tags are on his harness, and he can't have his harness on if he has his pack on. So I found a great tag online, I'm going to get it laminated and I will then sew it to the pack. But I was just wondering if I should make another tag that says what he's been vaccinated for?
Here's the tag I found online:http://www.wolfpacks.com/acrobatdocs/Pack_Tag_Male.pdf

You'd be best checking the laws in NS. I know here in the states, you'd want to keep the official rabies tag on his collar no matter what because if anything ever happened to him, that's the most important thing to have (if he lost the pack). A tag you made yourself stating he was vaccinated would be worthless to him because it is not an official tag and would most likely not be accepted by any vet or dog officer who picked him up.
On the pack, you could certainly have an ID tag any health issues (prone to seizures or needs meds) and the like.

Does the pack have any D-rings or other metal loops? If so, you can just clip the tags to it.
Here's an example of the kind of clip that will easily let you switch the tags from the harness to the pack. Tag clips and tag bags And if there isn't a good spot to clip them, then I would get/make something that says ID, put the tags in that, and put it inside the pack.