In order of asking: acrylic mirror is available from most glass shops and large sheet plastic distributors. Generally 1/8" thickness is the going deal but most of the time it needs to be laminated to a backer to avoid deformation and optical distortion (funhouse mirror reflections). Yrs. ago we put quite a bit of it in corporate aircraft, sometimes laminating the entire facade of galley cabinets, lavatories, sometimes full bulkheads. The "silvering" was very thin and very sensitive to scratching and also susceptible to solvents in contact cement. At that time, we sprayed the back with zinc chromate primer before laminating to avoid these problems. These days there is no need for this kludge as the manufacturers wised up and now apply a protective coating over the silvering.
The bumpers on the baking pan are 1"X1 1/4" by 17" plastic bars (no reason for nylon except we had some scrap at work, could be wood) attached thru the pan at each end with what used to be called saw bolts and are now sold as sex bolts. I used aluminum ones from the TruValue as the unslotted head on the female is very flat and thin and the pan is aluminum. Any panhead bolt and nut would work if you countersink the battens for the nuts. The bars simply elevate the pan high enuf that it doesn't rock on the stove knobs which in the case of my my stove are higher than the grates and keep it from moving fore and aft. Since buying this old trailer, I've got in the habit of replacing steel bolts and screws with stainless around the shower and galley area to avoid corrosion I think I got the aluminum bolts fo much the same reason.
The bumper is two parts: there is a black plastic extruded track and the safety- orange bumper which snaps onto the track to hide all evidence of attachment method. This was scavenged at work so I have no idea of the manufacturer or product name. I think you can find something very similar in Granger catalog.
As for the microwave
, aluminum angle bolted to each end of the microwave
shell and also bolted thru the floor of the overhead lockers. I removed the shell to use bolts and nuts but if certain of clearance inside the shell,pop rivets would probably be OK. As the leg of the angles which bolt to the overhead face inward (had to do this way as no extra space for a 1" flange next the stove hood) there's a little trick involved in both laying out the hole pattern and mounting the whole rig. I don't think it's necessary to go into detail as the way you finesse this sort of problem is a personal thing and depends on your experience and approach.