Take a look at Patagonia's Capilene 1 and 2 base layers. Pricey but often on sale. Under Armor is another popular brand. There are lots of other polyester wicking shirts around. Check the athletic (not sporting goods) departments at places like Target for less pricey versions. I don't think anyone wears polypro any more! Most polyester base layers are treated to resist odor and come in a variety of weights.

Lots of folks prefer lightweight merino wool. For one thing, it produces less armpit odor (more of a problem with men than women) than synthetics. Icebreaker seems to be an especially popular brand. Used as a shirt, it has a tendency to wear out sooner. Unfortunately Patagonia has discontinued their Merino series, a merino wool-nylon blend, lighter and longer-wearing than all merino wool. I recently got a Merino 1 long-sleeve crew neck on closeout. It's really nice (except for the ghastly green color) and very light (men's small is 4.0 oz.). but I haven't worn it in the field yet. A Google Shopping search may come up with some in your size.