The enlarger has a standard M39 lens thread and will take any common enlarger lens.
People will advise you to get the same enlarger lens they use themselves and so you will get emphatic advice to buy a Nikon or Rodenstock or Schneider. However, in reality there is little difference between them. They all make a budget 4-element line and a higher performance 6 element line. Meopta also makes the 6 element Meogon (I hope I got that right) that is highly thought of.
The Apo models need to be used at wider apertures to see any performance increase due to lessened diffraction, but then you will need a glass negative carrier and alignment becomes much more critical.
A Rodenstock Rodagon, Nikon 50mm f2.8, Schneider Componon or Meopta Meogon will serve you well. There are also good lenses from Fuji and Computar. Beseler and Omega sold Schneider and Rodenstock lenses under their own names, Omegaron comes to mind. Choose between them based on price and availability.