$95.
The only Pokemon tags left on HF are all G4/G5, but they're decently priced. The G1/2/3 tags are all upwards of $75. Make sure he'd actually appreciate the gift though, my friend thought "Species" was a stupid gamertag. Some people just don't value them. Can't really blame them, though.
Try buying him a main account with stacked stats for the games he likes. There are 15th+ Prestige accs on MW3 for $20.