Epic Cosplay is one of my go-to wig vendors. They are situated in southern California and have a nice selection of half-cap, straight-woven wigs. The fibers are heat resistant and durable. I've have very good luck with them! They have a nice range of colors and lengths, as well as some good pony-tail and bun clip-ons. Given the weave of their wigs, they don't have as many that work well for large, vertical spikes, but they are able to service most other styles.
Shipping times are accurate and prompt, and their customer service responds quickly. Did I mention the free shipping?