The translucent trackballs are less dense than the standard white cast polymer. A lot of BYOAC'ers like the translucent trackballs for aesthetic purposes, but they are actually a bit inferior to the cast polymer white trackballs. The white ones are heavier and have a better roll to them because they are more dense. I had the opportunity to speak with Betson-Imperial's VP of Sales, and I mentioned translucent trackballs. He told me that they only carry them because some operators and BYOAC'ers (he lurks here) request them, but they don't recommend them. I would have to imagine the same goes for the Happ translucent trackballs, but I don't know for certain.
I have purchased 3" Happ trackballs from Gatorcade before. In the past I've dealt with Pedro, and he ships very quickly (either that same day or the next). I've always received brand new trackballs still in the box from them.