I can't find the passage in question, but in general, I play parallel 5ths moving up or down a scale by alternating between 5-2 and 4-1. If you can't reach that stretch, then playing 5-1 and 4-1 is another option (in this case, keep the top line legato, and it will be okay if the bottom line is disconnected a little bit).
Either way, it's a little tricky because you need to be able to make that 5-4 crossover smoothly. If you're having trouble, you can practice that by playing scales using only those two fingers.
As it turns out, I was assuming that the 5ths were chords; I wasn't expecting them to be broken. In this case, playing 1-5 and walking your hand down the keyboard would be possible, but I would consider playing 5-2 when the lower note is on a black key. In this case, a rigid alternation between 5-2 and 4-1 would be fairly awkward.
I did neglect to add this disclaimer: since I have no idea how large your hands are, I'm assuming that they're about an average size for a guy who's about 5 feet 6 inches tall (coincidentally, that's how large my hands are). If your hands are smaller, you'll probably favor using 5-1 for all the intervals, and if they're larger, you'll feel more comfortable using 5-2. In the end, it's all about what feels best for you; these are just suggestions to try. In this situation, the fingering isn't all that critical, so feel free to experiment!