The Burnley striker has had two loan spells at Home Park, the second of which came to an end at the beginning of December.
And Fletcher has confirmed that the only thing standing in the way of a swoop is finances.
"He wants to come, we want him here. Verbally, it's all done," Fletcher told Plymouth's official website. "We have just to wait on the finances.
"We have got nothing to play with at the moment and we have got to see where we go with that.
"Like any business, you have got to run it properly. With all the trouble we have had over the past few years, there's no point in throwing money about.
"We are a football club with great traditions and we want to be here for hundreds and hundreds of years in the future, so we have got to make sure the finances are done in the right way.
"I'm sure the fans appreciate that and understand."
MacDonald's first spell at Argyle last season saw the striker net four times in 18 appearances and he added two further strikes this campaign in his 17 games.