The part you seek shows up on ebay every now and then. It is the filter cover and tool set holder.
I had to obtain one for my bike. But, I was not patient enough and overpaid. I would encourage you to check with the VJMC email members (free to join) to see if you can find one cheaper than ebay. If you are a bike flipper or rebuild and sell lots of them I am for some reason less willing to help those guys. Something about that seems disagreeable to me. Bill Silvers is on VJMC and he's well published and puts out requests for parts all the time for bikes he builds to sell or that people come to him for restoration. He used to do primarily the 305cc Hawks but now he does lots of other Hondas. Something about him or his flipping does appeal to me, so I don't respond to his parts requests and often ignore his posts. You can get the VJMC in a digest daily or weekly mode and traffic is not heavy, so it won't be stuffing your inbox.
I don't have a spare or I would sell you the spare.y
I believe they look so good because they are given a very thorouch cleaning and degreasing and repainted and side covers are either polished or repainted.
If the motor is torn down it is easier to paint or powder coat the parts and reassemble. Especially is you want to do a multicolor motor to highlight pieces or have the cooling fins black on the cylinders. Multicolor on assembled motors can be done just requires a good masking job to separate the parts which are not to be painted the color you are doing. Similar to the SOHC motors the aluminum used wasn't really great quality so many times attempts at polishing can provide mixed results if trying to achieve a mirror polish. The CA95 being older than the majority of the SOHC bikes can make it less likely to have good reslts polishing. Try it, you may not have a problem..if it polishes nicely great vcontinue down that path. So stock the cases and motors were painted for same reason most of the SOHC bikes were. If I recall correctly Cliff did a nice job polishing his outer covers and few other parts. Cliff does nice work.
As far as the petcock, lots are worn out and rebuilds don't work and they are VERY expensive if the rebuild kit doesn't work. Adapter plates to fit either a Pingel or other petcock are used. You can make your own plate if you are handy an either fit a turned on lathe adapter or just a heavy plate and gasket to seal to the tank and then drill and tap for a plumbing fitting to secure leak free to the plate. Then you can fit a petcock to that threaded fitting with the sock filter go into the tank. Or, use the petcocks with filter bowl to trap anything from reaching the carb. Another option is to go with the petcock that screws into a threaded hole, then you tap it for the threads you cut into the plate. The plate can be cut and dressed with grinder or files and drilled and tapped for the petcock or the plumbing fitting. A drill press makes it easier but, you can do it with a drill if you are careful with your drilling.
