How to book Gypsy for Gir Safari Officially

So i know that we can get a permit from the official gujarat government website but there isnt any option for booking the Gypsy or the Guide. The rates of both are however mentioned on the website and find it reasonable. I want to know if there is any way we can book the Gypsy and the Guide in advance or is it done on the spot? If so then is the availability of Gypsy guaranteed? Im finding the process very confusing as most of these services are being provided by Private portals who overcharge. The customer care number mentioned in the Government website is almost unavailable all the time. Its as if they want us to go through private bookings only. Please help since the process is confusing.