Didn't know about the 125. Do you know how old it is?
Ryobi made a couple of darned good planers during the early to mid
1990's The AP-10 is close to legendary for being one of the first really portable planers that worked well. The AP-12 is a 12-5/16" machine that is built like a fire plug and very reliable. I have owned an AP-12 for about 12-15 years and quite frankly I have abused it during the past year or so by running some very heave 8/4 timber through it . I eventually cracked the motor/gearbox housing but a good buttering with JB Weld pulled it back together.
I am not surprised that Ryobi doesn't know about it. They seem to forget about a lot of their equipment and their owners after a few years. When I bought my AP-12 the knives were around $15/set until they discontinued them. Then the aftermarket versions were selling in the $60-$80 range. If I were you I would start checking out knife availability now. Mine is old enough that the high-priced knives were probably going to require me to replace the machine. 5-6 sets would come close to buying a newer one.
BUT - The Delta 22-562 knives that fit the Delta 12-1/2" machine work fine in the AP-12. They have an extra index hole in the center (the AP-12 doesn't have a matching pin). I got the Delta recommendation from this group 6-8 years ago. If your machine is 90's vintage and has the quick-index knives you might get lucky.
RonB