Ticket Combat site has been around for a long time and some of the information is outdated.
The courts have decided that the existence of a Stop sign (applies to Speed limit signs as well) is proof enough that a bylaw exists and therefore the bylaw does not need to be brought to court and does not need to be produced. You need to prove that the bylaw does not exist.
So what you need to do is contact the municipality and ask for a copy of the bylaw related to the sign in question. Assuming it actually does exists then you just need to make sure that it is correct related to the charge you have.
If the bylaw exists and is correct then there is nothing you can do.
If the bylaw exists and is NOT correct related to the charge, then bring a copy with you to court.
If no bylaw exists, then you will need to keep some notes of your emails and phone conversations about who you talked to and what they said. It is very hard to prove that something does not exist, so I am not sure what the court requires in this instance. Maybe this information will be enough, but if not, then maybe you can you ask the JP to order somebody from the municipality to come and testify that no bylaw exists. I still do not know exactly what the proper procedure is, for proving it does not exist, but maybe somebody else has a better idea how to do this.