Chum lee wrote:
"Is there a reason why the same basic item can't be made to the same specs so any replacement will match the original?"
Yep. Many. People. Time. Location. Materials. Manufacturing. Money. They are always different and constantly changing. Years ago, at the dawn of the industrial revolution, Eli Whitney was credited with the idea of interchangeable parts. Until then, everything was individually manufactured by hand and no two items were alike. Even parts from similar guns wouldn't fit together and had to be custom fit, . . . . . every time something broke. As a result "National Standards" were developed. The SAE, ISO, ANSI, and, UL are current examples. As of today, things are a little better, but, as you've found, still far from perfect.
Chum lee
Of course, unlike the automotive industry, it's rare to produce more than a few thousand of any individual model. Cars that drop below 40-50,000 per year tend to get eliminated.
There may also be patents that they are working around. Possibly with good cause or possibly because they don't understand what they can get away with without violating the patent.