Though every tool in window cleaning is a specialized or modified design, sometimes it is for efficiency and sometimes it is for the tool manufacturers to make money.
On one hand sleeves, channels, handles, carbon fiber poles, etc. can all be designed specifically and solely for window cleaning. On the other, there are tools that you can use that are universal.
@Luke’s belt is an AWP carpenter’s style tool belt from Lowes. @Giles has an Unger belt designed with window cleaning in mind.
Search for and read the threads on Soap. There’s a fun rabbit hole to jump down. (Personally a Dawn Platinum guy. Cheaper and more readily available without having to special order from a window cleaning distributor. Sorry WCR. Yet the end results are perfect.)
I use a BlueHawk 3" retractable razor scraper instead of an Unger (or Moerman, etc) brand scraper, even though they do the same work, I don’t have to acquire a specialized holster from Unger for my Unger scraper. I just retract the blade and put it in my pocket or belt pouch.
Likewise with scrim, fish scale, or huck towels from the Window brands. Some people live by them and they are worth the cost. I get away with full terry cloth towels that I get at Harbor Freight since they seem to have the most dense fabric knit compared to the “terry cloth” found at Lowes or Home Depot. My finishing towel is actually a repurposed lint free knit hospital baby blanket. I get them from a distributor in Fenton, Missouri that sells them by the pound. I think the last package I purchased was $35 with shipping and it contained 40 something 18"x24" size towels. Over two years later I am still using the same towels. I haven’t had the need to open the second package yet.
ANYWAY:
You can purchase a special $15 3-gallon Ettore bucket designed with the “professional” window cleaner in mind. 
But, huh, the lid leaks. Ain’t that a bunch of s***. Or you can get a $4 5-gallon basic round bucket with a o-ring sealed lid, that we all know works perfectly fine since it prevents denser liquids like paint from spilling everyday.
Maybe I can return it. I know I don’t need to buy Ettore or Unger for that but I wanted to find something wide for my mop and with a lid. I saw that Ettore is pretty popular so I thought it’s the best quality. Can you tell me what bucket do you use if you use a wide bucket to fit an 18-inch mop? Thanks