Gray has been in the hunt for a new forward since the recent return of Connor Wickham to parent club Sunderland.
The Owls boss is also optimistic of boosting his central defensive options ahead of Saturday's fifth-round tie.
When asked if a new striker could be in place in time to face Charlton, Gray said: "Yes. We keep trying.
"When it's an emergency loan you're always relying on the clubs you're contacting not having any injuries or suspensions and you're hoping with your friendships and contacts with managers that they're willing to let them out."
Gray is also eager to bring in a new defender on loan in time for Saturday's match.
The Owls' recent signing Oguchi Onyewu (calf) missed the midweek home defeat to Wigan, while fellow defenders Reda Johnson (hip), Martin Taylor (knee) and Kamil Zayatte (ankle) have all been sidelined long-term.
"Hopefully I'll have a message on my phone and we'll have one in for Saturday," said Gray. "But we're always looking to strengthen.
"We've got to make sure we carry on the momentum, the enthusiasm that we've got and keep players on their toes as well by giving them a bit of competition."
Cardiff centre-half Adedeji Oshilaja arrived on a month-long loan last week and Aston Villa midfielder Gary Gardner is hoping to make his debut against the Addicks.
Gray added: "I'll only bring players to this football club that I think are better than the ones we've got and what they'll hopefully do is bring up standards and the quality of training as well."