Here is a 4.4mm eyepiece made from a new Edmund 8mm Lanthanum (N-LaSF9) ball. Planetary eyepiece enthusiasts have been discussing ball eyepieces lately, but to try one you usually have to make it yourself. This one is mounted in the casing for a 7mm Bushnell orthoscopic, which was originally adapted for astronomical use by Sheldon Faworski. The 7mm Bushnell Abbe ortho optics are also included. It cost me a total of $98.64 to obtain both items.
The apparent field of view and effective "eye relief" of this eyepiece depends on how far away you place your eye. I haven't measured carefully, but it sort of feels like my 4mm UO ortho but with about half the field visible at the same distance. Obviously it is intended for viewing details on-axis in a driven scope. It gave me a very nice view of Epsilon Lyrae at about 265x.
Asking $80 shipped to US addresses.