It seems the best way to find one is just to try some out. I tried a few here in West. Washington and never found anything better than the stock PRL. Since re-flashing my phone last week I haven't bothered changing the PRL to anything other than what Sprint says I should be using.
At worst, the only issue I can think will crop up is that you can't get a signal. Changing to a different PRL shouldn't affect your hardware at all.