Can I find out about compatible newer models of my Shimano chainring? I have an MTB that is quite old. The biggest chainring with 42 teeth is now done and I need a new one. It's a Shimano FCMC30, but it seems nobody is selling that new anymore. The chainring in question says &quot;Shimano Hyperdrive C&quot;.
Since I can't find the original, is there maybe a single chain ring I could buy that is compatible to my type?
If so, where would I find such information e.g. online?
si.shimano.com has Shimano's technical documentation.  Searching for your crankset FC-MC30 produces the Exploded View (EV) document https://si.shimano.com/pdfs/ev/EV-FC-MC30-1351.pdf
This lists the part numbers and descriptions of the components of the crankset. The good news is that your chainrings are bolted on and so are replaceable. A replacement ring must have the same mounting hole number and position (BCD - diameter of the circle of bolts). The bad news is that the large chainring mounting holes apparently fit a short-lived, obsolete standard that is unlikely to be found.
A recent reddit post is relevant:

semyorka7 6 months ago · edited 6 months ago
So, look closer at that diagram. STX FC-MT30 through MT33 were weird
shit - there's actually only bolts on the crank for the 58mm bolt
circle. both the inner and middle rings bolt through with the 58mm
circle, the outer ring actually attaches to the middle ring.
You can probably get away with a 94mm 5-arm outer ring, but the bigger
issue is that if you want to replace the middle ring, you need a NOS
middle ring - otherwise there's no place to attach the outer ring
Both MT32 and MT33 call out 94mm instead of 95mm for the outer ring,
so if you want to guarantee that a non-STX outer ring will bolt up
without having to do any work with a metal file, those are the ones I
would look for. Shimano PN 1SC3200
Unfortunately, people usually spend most of their time in the middle
ring and NOS middle rings for old shimano MTB cranksets are basically
unobtanium compared to outer and inner rings. Frankly I'd recommend
replacing the crankset with a nice 110/74 triple that you can easily
source a variety of chainrings for - FC-M730, FC-MT60, FC-M560,
FC-M900, etc are all plentiful on ebay.