So far, no references or period illustrations have been found for the practice of neck-carrying a knife smaller than the trade knives. Surviving examples of neck-carried knives from that period/culture are Native, and fall into the common range of sizes trade by the French and English. Once the frontier was crossed, traders were the only commercial/large-scale source for knives.
A quick check of my books and notes didn't turn up anything on archaeologically-recovered fixed-blade knives smaller than the 5" range (4 1/2"-5 1/2"), other than blades that were worn-out to the point of being "awls", or were broken or rusted away. The blades less than 5" were all from various folding knives.
There are very few references to the carrying of neck knives by Euros; most of those mentioned are French, in Canada. Most of those references describe was carried when preparing for war, and the people mentioned are mostly settlers. For the most part, period descriptions of every-day attire and equipment don't mention neck knives.
In other words, you probably won't find much documentation of small knives (because they didn't seem to be there) worn around the neck by coureurs du bois (because it didn't seem to happen).