I’m a huge fan of dynamo hubs, but if this is just for one trip, I think you’re probably better off just using an external battery. ...unless you happen to find a dynamo wheel on CL for cheap between now and then. I think the company Biologic makes a rectifier device that goes between the hub and battery that allows you to charge thing and if’s only $30 or something like that. That’s the cheapest I’ve seen. Some cost $200. You could probably have this set-up working for $100 if you find a used wheel, but going new and nicer parts you could be in $400 real quick depending on what you want. The plus side on the dynamo is that if you ride at night regularly, you’ll never have to worry about light issues again. Just bolt a dynamo light onto your bike and you’re good to go.