Were you planning on putting your own information on the collar? Like, he's your cat?
Great idea. Just put your phone number on it with one of those indelible pens.
The only collar I would consider is one that breaks apart under stress; you can get them at Walmart and pet stores. Dollar store collars don't break apart. Please don't put one of those plastic Hertz flea collars on him, the chemicals in them are too strong.
If you know someone with a cat, ask them to buy you a dose of Revolution at the vet's (since the vet might not give you one without seeing the cat). It's a tiny amount of liquid that you apply to the back of his neck. It also takes care of ear mites and some worms, which he probably has; most strays get them sooner or later. It can be repeated a month later if you think he needs it.
Poor guy, he's lucky to have you.