Wolves striker Griffiths, Manchester City defender McGivern and midfielder Claros, whose parent club is Honduras' Motagua, are due to leave next month, with Hibs attempting to extend the deals until the end of the season.
Speaking ahead of Sunday's Clydesdale Bank Premier League fixture at Kilmarnock, Fenlon said: "We are working away, but we can only do so much. The final decision is outside of our control."
Fenlon is focused on Griffiths, McGivern and Claros before determining whether any further transfer window activity will take place at Easter Road. He added: "They're the ones we're actively trying to sort out at the moment."
Midfielder Gary Deegan could start at Rugby Park after making his first appearance since suffering a fractured jaw when Hibs lost 3-2 to Motherwell last weekend.
Fenlon said: "He's got a chance. He got 75, 80 minutes this week with the under-20s. He's trained all week as well so he's champing at the bit to play."
Right-back Tim Clancy could be in the squad following a groin problem, with captain James McPake suspended following his sending-off against Motherwell on his return from a back injury.
Fenlon added: "Tim has been back in training. He'll train again Saturday, but it's a little bit early probably to be throwing him into games. Hopefully in the next two or three games he'll get some game time. We need to be careful with Tim, to make sure when we get him back in we don't set him back."