I believe they're out of Thailand, well that's where the GV I saw got their lift kit from and I think they did a bulk order with the sliders too.
These are the only sliders I have personally seen (there could be others, I just haven't seen them) that fit the new GVs with doors that cover the sills.
You're going to have to do some googling to find suppliers, sorry.
But they look like this;
