Well, my experience has been pretty different than others. I find the old Bo parts are really easy to find with the exception of a few critical bits. You can find them in every junk yard in the country, and plenty of aftermarket support too.
Now, the exceptions are the pitch change bearing for the elec prop, and the blades. If you want a new sector gear for the retract, you are gonna pay, but if you want the whole gearbox with a sector gear inside, it's about $3-500 for a working one.
Also, most of the wear items on the Bonanza are sourced from standard stock items. The retract motor is also used on Buick and Hudson wipers, the bearings in the center pivot yoke are standard SKF bearings, the cables are standard size and can have ends swaged as needed. Nothing fancy except the door latch, hinges, and some other exotic bits inside the E series engine. Lucky me, I have two engines sitting on pallets with good cams, all I need are bearings and jugs from an O-470R and good to go.
The splined crankshaft is going to be the death knell eventually. There are two STCs for swapping in an O-470 engine but they are rather pricey right now. Hopefully another engine STC will come avail for reasonable money. Hey, that sounds like a good summer project!