I use my reins. If they are long enough you can use them to create some energy by spanking them back and forth in front of you. One of the nice things about a split rein, they make good motivators
I also have a short (about 2 feet) of braided leather that I carry if I'm on someone who needs it. It has a clip on one end so I can clip it to my saddle. Anything like that will work, even a short rope. Just twirl it next to you, you don't need to even make contact with the horse. This is usually enough to get one moving.
If you don't have the money or time to get something like that, try slapping your leg. That's enough for some horses. I would forgo the spurs for forward motion. That is not what they were designed to do, although it is often depicted in cowboy movies. They are primarily for getting a horse to move off your leg in one direction or another, not to get them to move forward. Errrr, unless you're a rodeo bronc rider
Here is a very