alternative keyboards
Virtually all USB and Bluetooth keyboards work just fine with Macs.

There are about a zillion Mac-compatible keyboards, and just because one person loves a given model doesn't mean it will suit another (I still use my Apple Extended Keyboard, for instance). Some of the bigger makers in the field are Kensington, Logitech, Macally, Matias1, and Adesso.

What in particular (besides bigger arrow keys) matters to you? What do you hate? What do you love? Do you want wireless, or is USB ok?

You might want to check out these two Macworld articles: 


Review Roundup: Keyboards and mice
Keyboards buying guide


1 I bought a Matias keyboard. I hated it. I don't recommend them.