If you want to keep straight valve stems, you can use this device.
Makes inflating tires a breeze.
I've had mine for about a year and used it many times. Works great.
13 bucks at Amazon. Here's the LINK.
I just looked up the 90-degree valve stems on the No-Mar page and they were $17.95 each. I bought them from No-Mar at an event so there wasn't any postage or handling. They also have a cheaper, painted 90-degree valve stem for $4.95 but I don't know anything about those.