Striker Reid is on loan from Sky Bet League One club Fleetwood Town and that deal has now been extended until November.
Keates has explained that it is in the club's best interests that he has something lined up for when he does return to Highbury.
The Red Dragons boss is preparing for Saturday's fixture with Tranmere - and says improvement is needed from the last home game against Guiseley.
"I have always said I wanted four strikers and we have got four strikers here, but I am mindful of the fact that Alex is returning to his parent club in November," said Keates.
"So it is something that we need to put in place and we need to look at options that will give us that extra space to fill, that slot when Alex goes.
"We will be looking at any players that can strengthen the rest of the squad going forward," he told the Daily Post.
“We have got a couple of trialists in this week to have a look at and run our eye over, and we will go back and watch them at the clubs they are at."
Keates took the positives out of the home draw with Guiseley last week but knows his team will have to be better when they travel to Prenton Park to face Rovers this Saturday.