Putting The Hard In Hardware Store

I've honed my handyman skills in the past year, thanks to a storm-broke home that needed fixing and upgrades before going on the market and a new home that had all kinds of surprise problems, such as lots of leaky plumbing, non-existent weather stripping, a lumpy laminate floor, etc.
Every weekend, I try to put a dent into the problems at the new house. The fountain of plumbing problems have been contained. The shed's smashed-up roof - complete with what the neighbor said was seven years of pine needle buildup - has been patched and cleaned off. Light fixtures have been repaired. Bathroom fixtures have been installed.
I've still got the lumpy laminate, but I've figured out how to fix it and will do so when I've got the energy to rip up a floor.
What I haven't figured out is how in the world some of my home-repair needs can't be satisfied through those monster home-improvement stores.
Myriad windows around the new house need new latches, window screens, stripping and those little cross bars, which I'm told are called "muttons."
However, I've yet to find nary a latch or mutton at the several home-improvement stores I've visited.
And if you want a screen, you have to build it yourself.
That's right. You can't just go to a store and buy a screen. You have to buy the screen, the frame and a cutting tool and build the damn thing yourself.
Considering I seem to be a measure-once, cut-twice kind of guy, this little project rather scares me, considering how much the materials are.
I suppose windows have grown so customized over the years that the home-improvement stores gave up trying to stock already-built screens.
You'd think we'd have learned something from Henry Ford and his standardized car parts.
Oh well. I suppose this weekend I'll be adding screen-building and perhaps mutton-making to my handyman resume.