yeah the hoodman 3 is pretty good.
the cheap lcd viewfinders on ebay don't have an adjustable diopter i don't think.
if you have a rail system i found i could wedge the hoodman up from below so it presses on the rubber eyepiece, i have a gini rig and 1 of the 90 degree connectors pushes it up from the bottom a treat.
the cost of the hoodman holders is a bit crazy, redrock micro do a simple one. (link below)