Pardon my lack of frame knowledge, but I found a used steel road frame that I like, but the rear deraileur tab on the back is gone and has since been used as a fixie. Is there anyway to get a rear deraileur on this thing (I admit it, I like gears)? Can a new tab or piece be welded on by an appropriate shop and would it be reliable? Or is it impossible? Thanks for the education/suggestions.