I love a nice pen. I even bought myself a Mont Blanc fountain pen when I was about 20, which I still have and use. However, clearly I am in a minority. Pens imho are generally too personal for someone else to choose. Why does your mother want to buy him a pen, unless she is a pen lover herself (with her own idea of what to buy).
As above, a nice pen, worth keeping, cherishing and importantly using, can easily be found for £30.
How about a rucksack or a tent with the remainder?