Though I only used one of these for work for a week, I was very pleased with it, especially for the price.

http://www.theronoptics.com/SAKER_ED_60MM_SPOTTER_HKQ5.php

I like it more than any other spotter I've used in the price range you've proposed (Burris, Nikon, and BSA).

Don't forget to get him a good tripod and head to go with it!

Sounds like a great gift idea.