MoonSong
Rules-lawyering drama queen but not a munchkin
Maybe a PC spell caster can cast Darkvision on the halfling. I'm with MO on this one. Don't just give her the googles. Ever. At best, allow her to acquire such an item by her explicitly getting an NPC to craft it for her, or for her to go quest for it. I really could not imagine a player wanting darkvision so bad that she would ask if she could remove the eyes of a darkvision creature and replace her PC's own eyes with them. That is so weird that someone would ask a DM that.
But if she really wants to have them, and is working towards that, even trying to think outside the box to get it, she should get it at some point. Letting her try well knowing you will never allow her to succeed is deceit. If MO doesn't want her to have darkvision out of principle he should have told the player -look no matter what you try, they didn't give halfling darkvision for a reason, short of you getting someone to cast darkvision on you or going warlock you will never get it, you won't find the goggles of darkvision for sale or for loot ever. It doesn't exist on this campaign, period. And the thing with the eyes, I don't mind you trying it, but I will never let it succeed- Honesty is better than just letting people get illussioned over something. Make it hard, make it important or whatever you fancy, but allow her to get it at some point and let her have some fun with them -the only thing worse than never getting it would have to be receiving the goggles as a final reward the very last day of the campaign when there is no way to enjoy them-.