Large gate for concrete wall

I have a concrete block wall in which I would like to install some kind of large gate for access into my back yard. I had in mind that it would be about a 70" entry or more. I think that a sliding gate may work best, but hinged would be acceptable. The idea is to allow access for brush removal, a stump grinder, things that are too large for a standard garden gate. I have searched many places, but I can't seem to find anyone selling such a thing. Do I have to build it from scratch? If someone could point me to a manufacturer or give me some ideas I would greatly appreciate it.