British and Irish Lions wing North is out of the tour after tearing his hamstring in the 39-21 defeat by the world champions at Eden Park.
James, 29, and Walker, 24, start on Tuesday against the Chiefs in Hamilton.
"There's an opportunity for both of them, absolutely," said Gatland.
"For the players that are playing tomorrow night there's a lot on the line in terms of personal performance and team performance before we name the side for Saturday."
North, 24, suffered the injury tackling Waisake Naholo late on in Auckland, where Wales led with 18 minutes remaining before succumbing to a 27th consecutive loss to the All Blacks - a winless run stretching back to 1953.
Northampton Saints' North has been released from the Wales squad and is returning to the UK for further treatment.
Gatland is also without Lions backs Alex Cuthbert and Leigh Halfpenny, who are both recovering from injury.
Hallam Amos started on the left wing against the All Blacks last Saturday, with Liam Williams at full-back.
Gatland could select either Walker or James on the other wing for the match in Wellington, or he may decide to move Williams across and put Gareth Anscombe at full-back as Wales target a first win over New Zealand on their own turf.
Ospreys' Walker won his solitary Wales cap against Ireland in August 2015, while Cardiff Blues' James was recalled to Wales' squad for the 2016 Six Nations having not won an international cap since 2010.
James scored six tries in 13 appearances for Cardiff Blues in the 2015-16 Pro12 season while Walker crossed four times in 12 games.
Wales have also called up uncapped 18-year-old Ospreys wing Keelan Giles as cover, but he does not arrive in New Zealand until Tuesday.
Gatland has named an entirely new XV for the midweek trip to the Chiefs, who are two-time Super Rugby champions.
"It's a real challenge for them and gives them an opportunity with a good performance to potentially put their hands up for the second or maybe the third Test," said Gatland.
Gatland said it was "tough" to have such a short turnaround between matches.
He added: "For a number of players, if they're involved next year with the Lions, they're going to get that every week as well.
"It's part of the toughness of touring New Zealand."
Wales coach Warren Gatland says George North's injury gives wings Tom James and Eli Walker an opportunity to earn a place in his side to play New Zealand in Wellington on Saturday.