Visit a big box hardware store like Menards or Home Depot. They have displays of patio doors of several styles. Brouse these to get ideas, then search on-line. You didn't describe the problem with your doors. If these are balky to slide, it is possible that a little manitence will fix it. Sticky, balky patio doors are often caused by dirty tracks and rollers in need of lubing. Clean these up and apply lube to the bearings of the rollers, and you might be pleasntly surprised. Study the construction of your doors. Some models can be lifted out of the bottom track, then the bottom end of the door moved to disegage the top from its retainer track. Get help when you do this, These doors are HEAVY and you could end up dropping one, and or straining yourself.

Thanks for the info everyone. I had a chance to see a full sized example of sliding panels in a fabric similar to one I'd liked in a sample book. But seeing it in real life was an eye opener. It looked very cheaply constructed and was just plain nasty! And this was from a company that quoted over $700! Instead, hubby and I liked the vertical cellulars and I'm in the process of getting quotes for those.

That's what I had to do when I did this fix recently. Remove the screen, remove the stationary panel, remove the sliding panel. I then removed the rollers and determined what size to buy, but because I didn't have the time to go get the rollers that day, and didn't want to leave the opening open overnight, I reassembled the door, with the broken roller. Then a day or two later when I had the replacement, I didn't want to go through the same effort to remove the doors, I tried lifting the end of the door with the bad rollers (carefully) and used a mini-prybar and a small hammer to tap the bad rollers out of the slot. This may only have worked because I had already removed it earlier, so that it was less stuck in place.

Is there anything else wrong with the door? Rollers can be fixed/serviced quite easily in many cases. As to your question about a 4' French door, I would be cautious about that. French doors are notoriously sensitive to operation and size. A 4' door, hanging out in space, hinged, and heavy (i.e. full glass) is a recipe for operational difficulty in my opinion. There are plenty of sliders that can be opened with a single finger's effort. I think you need to see one of those type doors and feel the operation on it to make and apt comparison and then decision.