What Manufacturer are these?

Google finds 23,000 hits for "encore+florescent+lighting". The most promising is:

Though they may not still make that style.

Colbyt

Take the cover off the end. What you have probably looks like this:

If not exactly like that with the cover off, take the burnt one to your local Lowes or Home Depot.

I may be all wet on this one, but they look like fairly ordinary eight footers. Haul one down to the HD (like the other fellow said) and I bet they fix you up good. Get you going.

Then, expect to pay a hefty disposal fee for the old ones to haul off.

NOT common. These mounts are flush mounted to the flange. Look at the photos.

They require disassembly, a 2 man job, just to get at the mounts. The ring has studs behind them which are bolted to the face.

You are all wet. These are NOT common 8 footers. They install in pairs at a fixed right angle, with 2 together to make a square. The local electrical supply houses have never seen anything like them.

The 3rd one down looks like it, but they seem to just pop in place, but the existing ones seem to be bolted in place. As soon as I find the tall ladder again I can check this out.

Why ask for help if YOU know all about it? And if you need a tall ladder common sense would tell the ordinary smart person to take it out for comparison while you are up there the FIRST time.

BTW: I've been doing commercial maintenance for 15 years. And this IS a common end despite the layout of the bulbs

When I looked up there the first time it looked like the sockets were bolted in place and to get to them required another person to help disassemble the fixtures.

If it is a common end, why doesn't the large electrical supply house even know what they are? Nobody in this large city knows what they are and nobody carries anything like them locally.