Depending on the workplace, Hawaiian shirts or bowling shirts are also great (I have a couple with dragons on them and I love 'em). Lightweight, short-sleeved, fun patterns.

Alternately, a hoodie vest is a good middle-ground and I can wholly recommend Mishu's: https://www.mishuboutique.com/collections/mens-outerwear The Alien Geo in teal looks rad and is super comfy. I got one at a festival and had to order another as a backup.