If I remember correctly, these are only found on early cars (to 70?) so they may not, in fact, be necessary at all. Hopefully someone else who has more recent 140 experience than I do can confirm this for you.

If the ones you have now are still intact (roller is still round, reasonably smooth and rotates easily) I would try to overhaul/improve them, by a thorough cleaning and perhaps sanding with fine sandpaper (but be careful not to sand too hard or unevenly and make them out-of-round) 0000 steel wool might be suitable for cleaning them, them wash to remove the oil the steel wool leaves. Lubrication is a tricky question, as you want them to turn smoothly, but grease of any kind on the outer surface is what makes the streak on the glass.

I am surprised these parts are still available, either from Volvo or aftermarket.