I have LaCrosse 5mm for the cold water and air temps, Hodgeman 3m for warmer early spring temps, ProLine breathable waders for early to late summer, a shortie and long wet suits for the times I want to get wet for over a couple of summer hours. All my waders have boot foot with cleats...I do not want to cross contaminate the ponds I detect in with anything that might cling onto the felt soles. I do not want to put on a second "shoe" as is the case with stocking foot waders. I have owned Simms, LLBean and Orvis breathables. Most waders have lasted about 600-800 hours of detecting with leak repairs. You will need to learn how to find and repair leaks.
Right now I have found the LaCrosse, ProLine, and Hodgeman models that are cut high enough, come tight under my arm pits with bibs in front and rear, are best for me. Some waders are cut shorter and are straight across the front, back and under arms. They tend to let ocean splash get me wetter the the higher bib cut. The boots I have bought did run true to size - I use 12 for summer and 13 for winter - room for extra socks. I stayed away from the rubber and tri-laminated waders as they are heavy and not as flexible as other materials.
Notes:
The "breathable" waders do not "breath" when under water.
Neoprene waders are easier to find and repair leaks in. You will sweat more in the neoprene waders.
You will sweat inside the waders, up to a couple of quarts, depending on your amount of effort spent in digging. This has been misinterpreted as a "LEAK", it is not!
I also have a 1.5m neoprene jacket with zipper front that I wear OVER the waders to keep the ocean spray / splash from getting me wet in the colder months. I bought the largest I could find - a XXL and it is very tight over the winter 5m wanders. With a bit of tugging, it will stretch and it works well, plus it adds a bit of warmth. I bought the short sleeve model so I can put my gauntlet gloves on then the jacket to keep my arms and hands dry. It is 100% especially if you raise your elbow above your shoulder, water will find a way in.
As for source: LLBean, Orvis, Cabelas, Bass Pro, Dicks and eBay. (Kmart several years ago.) I have made purchased in store and OnLine and from ma and pop shops; it I needed a pair and they fit and felt good...I bought them.
I think this covers all your questions, if not just ask another.