Thanks everyone for the advice!
I went with the NP open palm mitts, and am really happy with them. Adventure sports still has them on sale for $25, so you really can't go wrong: https://adventuresportsusa.com/np-split ... -palm.html
Had them out for two sessions. FIrst session was 58F air and 44F water. I didn't really even need gloves at 58F air temp, but wanted to give them a go. When you crash, they are going to fill with water. 44F water is pretty cold on your hands, but all the water comes right back out and then your hands warm up very quickly. Tried one hand with the open mitt, one without, and the one with the mitt definitely warmed back up much quicker. I really liked that they fold back on your wrist completely out of the way when you're not using them.
Today went out in 42F water with 49F air. Wind was 15-20kts, riding on race foil with race kite, so apparent wind was 30+ when going upwind. I was only out for about an hour, but my hands were plenty warm. The few times I crashed, that 42F water is COLD on your hands, but as soon as you take you hands back up out of the water, they warm right back up. It was nice to be able to blow warm air into the mitt, and then I was back up riding with comfortably warm hands.
I think these will be my go to gloves in over 45F air from now on.