they are A4tech lk optical switches (not traditional mx) - relatively error prone and can be found in a ton of budget optical chinese no name brand boards on amazon.
the shape is due to the light beam that passes through the switch
they arent really available anywhere that im aware of - easier and probably cheaper to simply replace the entire board. the entire board sells for $40 new.
Save yourself a TON of time drying and get this thing: https://www.amazon.com/gp/product/B008H2OELY/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1
Takes less than two hours to completely dry.
There may be some cheaper/better options out there but this is what I use:
https://www.amazon.com/Magnasonic-Professional-Ultrasonic-Eyeglasses-MGUC500/dp/B007Q2M17K
I found that since you cannot adjust the Hz level/power setting, sometimes it would take me a few 8-minute (longest setting) cycles to get my dirty stabilizers cleaned. I think this would be more than enough to clean your switches, stabs etc.
Yes 5mm and these are the ones that were recommended to me last year: https://www.amazon.com/ThreeBulls-120Pcs-Dampeners-Keyboards-Dampers/dp/B01N75JL0F/
Personally, I didn't love the way my keeb felt with o-rings on the switch stems, and it only helps with the downstroke noise, not the upstroke, so I ended up just getting some silent switches instead. But as always YMMV!
SOLUTION: I actually kept the new tangie housing and bought some cream clones from amazon and they sound and feel almost exactly the same as the real thing. Worked for me. Worth a shot.
Amazon link below
i use these https://www.amazon.com/gp/product/B092MB697H/ref=ox_sc_saved_title_1?smid=A20HYALX66GUT&psc=1
one or two in the hole (depending on pole length), and one on the outside of the switch, below the pole. it works way better than a ball bearing. the sound is loud and very poppy.
i use these on the stem pole of switches that need a boost to the spring. it basically preloads the spring without adding much weight to the overall stroke. also works the same as silencing o-rings but is internal.
other option is to lube the stem legs and leaf contacts.
https://www.amazon.com/gp/product/B000MNBOGY/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1
Yep, not great but it works; even with 45g bottom out springs which are very close to Gateron Clear 35g actuation springs.
The non-slip shelf and drawer liner I have isn't nearly as uniform as yours was and very compressible; it took shoving one little square into each side between the click jacket and stem. Messing with it for a few minutes I still couldn't get it consistent but worst case it mutes the click and best case it feels like a jailhoused tactile switch.
I just got my second batch of 1000 002 o-rings for about $15 on Amazon and have made another 100 or so jailhoused switches for my next couple projects. The beauty of these is you pry off the click jacket, slide them to the top of each click jacket hook on the stem, snap the click jacket back on and go. Some switches need the spring or click jacket orientation flipped but for the most part they are very consistent. If your liner squares start moving around or changing with humidity and temperature I'd recommend them.