Get yourself a golf type collared shirt and have your logo/name embroidered on or have it screen printed small to the right or left where pockets usually are on the front. On the back have screen printed in large black letters event photographer and under that in smaller text the website where pics can be seen (www.seeyourpichere). If you make a badge you could have major issues with the event promoters unless you know them or you have pre authorization. I had the newspaper where I worked years ago make me up shirts like this as I covered a lot of events for their website where they sold the images.