This may help:
Grease compatability chart
If you want an all-around premium grease that's easily available, use Mobil synthetic.
If you need something more affordable, considering the volume of grease you'll be using, you'll do fine with any lithium-based, NLGI-2 grease with EP additives. It should state it as such on the container. It is available almost anywhere grease is sold over the counter.