How to rescue a Hollandaise with too much lemon
Yes, do it. Making the second batch is your best way to get something good. 

First, keep your first batch warm, don't let it cool down. Second, you don't have to wait them to get ready to mix them. Start with the new yolk with a bit of water, beat until foamy. Then, instead of drizzling oil, drizzle the old batch, until incorporated. Then add more butter. Use a lower temperature than for the normal beating process, so you don't overcook the yolk from the existing batch. 

Alternatively, if you don't mind having a fattier sauce, just add more butter to the existing batch. The fat absorbability of hollandaise is not limited by the yolk emulsifiers, but by the available water. A single yolk can absorb liters of fat, if you started with a bit of liquid before adding the butter.