Because CP Air no longer exists and hasn’t existed for over 20 years now, the amount of collectible items available relating to the now defunct airline is not very large. Sure the full history of Canadian Pacific airlines goes back farther than the CP Air era but compared to other giant historic airlines like Pan Am & American, the fan interest in CP is much more likely to be a lot smaller and specialized being it a relatively obscure Canadian airline who only a lucky few may have flown.
For many years the only real CP Air collectible you could obtain was by building it yourself in the form of a model airplane. Plastic & resin model kits have been around along time and are of late becoming a dying hobby and art form but true enthusiasts are still around. It was as simple as buying yourself the correct model airplane and the proper decals and paint, the rest was up to you. There were an infinite number of model kits and decal kits available so you could pretty much make any CP Air model you’d like. After that there wasn’t much else.
Nowadays high quality and detailed diecast metal model planes have become extremely popular amongst collectors. Many companies are now producing entire fleets of planes from airlines past and present including of course, CP Air. Some of the companies that have produced CP Air collectible jets in various scales that I know of are: Inflight, Aeroclassics, Corgi, SkyJets, Gemini Jets, Herpa & Dragon Wings. Currently all of CP Air’s planes have been represented with their orange, red and silver paint schemes and special additions (Expo 86 & Montreal Expo logos). Models of course are a highly collectible reminder of the good old days but at your local aviation hobby shop you may get lucky to find other CP Air specific products for sale such as a custom made model, picture/print/poster or even a hat, pin, t-shirt or luggage tag commemorating the airline. There were also several books written about Canadian Pacific Airlines. One very good one but long out of print is D.M. Bain's "Canadian Pacific Airlines - It's History & Aircraft". More recently Peter Pigott's tribute entitled “Wing Walkers - The Rise and Fall of Canada’s Other Airline (Harbour Publishing) details the history of Canadian Pacific Airlines and obviously covers the CP Air era of 1968 to 1986. This book can still be ordered through various retailers or the publisher.