They are simple chain driven setups with a geared motor. You can get reasonable size geared motors from Surplus Tronics in Auckland. Or use a driveway sliding gate motor which has a rack so you can easily retrofit to a normal door, suggest Easy Gates in Tauranga. Or a sectional garage door opener.
From Easy Gate you can buy just the controller board. They are old designs, as they all are, but does the job and has all the inputs you need. And pin-in-hole components so you will be able ot hand solder any mods you want to do.