Vivitar Ultra Wide and Slim. Plastic 24mm lens, really pretty ok considering. Frequently seen on eBay for between 4 and 25 bucks. I had lotsa fun with mine. Or any old fixed focus plastic lens cheapie with "panorama" crop mode. I made some 6" by 18" enlargements from stuff I shot 15 years ago with one: really quite a bit better than I expected. All from a European trip I had bought a Rollei 35 for. The Rollei died on the first day of the trip, the Agfa "panoramic plus" soldiered on. Plus pocketable and 35mm is cheap. Not all labs these days handle the old 35mm panorama mode, though, but many will.