Clark, a 19-year-old winger from Southend United, joins on a work experience loan (similar to Dan Humphreys) and is seen as a player with a lot of potential.
Manager Dale Brooks said after capturing Clarke: "Alex is a player who was then coming through when I was at Southend and is a player that I think has a lot of potential. I think we can give him an opportunity at Lowestoft to really show what he can do."
Machaya, 20, is seen as a diminutive player with bags of pace, has played for Norwich United and Thetford and joins on a permanent basis.
Brooks said: "Emmanuel is a player who is looking to better himself. He just wants an opportunity to play and we're happy to give him that."
Both players are available for selection for tomorrow's visit of Staines Town.
Updated 17:43 - 26 Jan 2018 by Sean Galea-Pace