My approach is based on Norbert Bruggens book and I use a 4mm stainless steel shaft with a Simrit seal. (This is a lip type oil seal.)
They are very reliable and seem to last for years. Points to watch are to oil occasionally and try to keep the rotational speed below about 2000 rpm to minimise wear on the seal.
I "sandwich" the oil seal between two brass plates and incorporate a ball race just behind the seal on dry side.
Works well for me!
Any commercial products recommended?