Dressage Extensions has Ice-Fil shirts on sale. Don’t forget to wear sunscreen under your shirt, though. I find the sunblock material too hot. The combo of a regular shirt and sunscreen is better than sunscreen alone.
Columbia, Mountain Hardwear or North Face button-up shirts. Columbia has the Silver Ridge shirt: http://www.columbia.com/womens-silver-ridge-long-sleeve-shirt-AL7079.html. MHW’s is the Canyon shirt, http://www.mountainhardwear.com/womens-canyon-long-sleeve-shirt-OL5859.html. And North Face has a bunch. This is one of them: https://www.thenorthface.com/shop/womens-shirts-casual-tops/womens-long-sleeve-shade-me-shirt-ce3z?variationId=FJM. Kastel Denmark is good too.
