A lot of good questions here. I learned to fly on a Kadet Jr with a Veco .19 in the eary 80's

It was a fine airplane, and a good trainer in its day. Several reasons it isn't produced anymore.
* It was a 3 channel model, at that time there was debate whether a beginner should start with an aileron trainer or not. Now 4 channel trainers are the norm. Rudder & elevator worked fine for control on the Kadet and Kadet Jr.
* It was a kit. Folks built back then, many do not these days-especially trainers. Cheap, good quality ARF's are what folks tend to train with.
* There are very few .20-.25 size kits (or arfs) period these days.
* The Kadet Jr does have a sort of a spiritual successor in the SIG LT-25. Bigger, with ailerons but still aimed at the 25 size engine.

Clear dope was commonly used to adhere covering and fill the fabric then colored dope used to provide...color. Dope is still used by vintage modelers and scale builders, but 99% of sport models are covered with Monokote, Ultracote or similar coverings.

Don't fret the cost of pins or hardware at the hobby shop. All of them are struggling to survive in todays world of internet commerce. Look at it this way, engines and radios are bargains compared to what they used to cost in relatve dollars, and so much better quality...