DH has been buying from
Dripworks. Don't get the cheap compression fittings for the large tubing that feeds the small tubing, only the most expensive connections have worked. And don't cheap out on the pressure reducers. It's helpful to put a knife valve or two inline so you can adjust things. But you can get the main line tubing from the big box home improvement store locally and save some shipping. I like it because now that the main lines are down, I can change the drip fittings as I see fit without help. Me and a sharp pair of garden clippers. For vegetables I like the adjustable sprayers better than the gym rated dribblers, but it might be soil-type dependent on how well the water spreads.
ETA: we have about 30 4x8 raised beds and we run that on 4 separate main lines. Not sure how that translates to 50' rows, but I kind of doubt you'll get enough pressure in the system to run the whole thing at once. If you pressured it up enough to feed all the emitters, the larger connectors would likely blow out.