First, if you have a fear of something happening to your gear, insure it. In my backpack there may be as much as $5-6,000 in equipment at a given time. Without insurance, if this were stolen, I wouldn't be able to replace it quickly! With the insurance (after the shock of losing it), UPGRADE! Second, there are several ways to carry an extra lens. You didn't state what telephoto lens you have, so its difficult to give a precise answer, but my DW has a 55-200 (kit) that she just puts in her purse. I have carried the same lens in the cargo pocket of my pants/shorts. My 70-200 f2.8 is much larger so that goes in my backpack. Because you want to carry only one extra lens, you could get away with a small backpack. If its a small telephoto, then maybe a belt case. Third, as far carrying it around your neck and looking like a tourist, that's a mindset. I prefer to look at myself as an enthusiast with half-way decent equipment. I use my BR strap, which you don't often see the average 'tourist' use. I hope this is helpful. Have a great photo day!