Get (something like) an Apple wireless keyboard with numeric keypad

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.}

Keyboard Maestro might be your thing. Make a new command group which only applies to the application in question, then for each key you want to remap, make a new command with a hotkey trigger set to the real key and an "Insert Text" action set to what you want the key to be.

The only shortcoming I've found so far is that it can't handle the in-built volume control keys on an Apple keyboard. It can detect them & act upon the event, but it can't suppress the volume change. In fairness, nothing else can either. Most programs I tried can't even detect it. Keyboard Maestro is the king of the pile.