I carry a nailclipper which has a small knife and scissors folding out of the body, on a chainring. The knife is only a bit longer than an inch, used for sharpening pencils for sketching. I can't imagine that it would be illegal. I bought it from a local farm machinery supplier, who had a small showcase full of the products of the firm, whose name now escapes me and isn't on their products.
A much more lethal instrument than a pocket knife is a common craft knife, even the surgical scalpel commonly found in artists' kits to sharpen pencils, trim paper, etc (I have a safety version by Morton Swann in my studio kit that I rarely use for fear of cutting myself).
Andre Jute