I have looked at homebrewing an FM 2-meter XCVR and already got help from
this group. The goal is to spend time on something that others could
duplicate and not work on a one of a kind.

First, why homebrewing ? Two reasons:

1) It is homebrewed
2) There is room for a "powerful" microprocessor that will do other things
(APRS is one of them)

It seems that the problem is the selection of components that can be sourced
in relatively low volume and at a reasonable cost by amateurs (read:
Digikey, Mouser and alike).

Here is what I have found some far:

1) Transistors for RX front end: relatively easy to find if based on
dual-gate MOSFET
2) RX band filters: I have decided to have a fixed capacitor and adjust the
inductor.The availability of adjustable coils (Toko for example) has
decreased in the last few years. Digikey only stocks a few of them but that
should be OK in the near term.
3) First IF filters: not much choice since 10.7MHz and 21.4 MHz seem to be
the only 2 frequencies stocked (most commercial boxes use between 35 and 70
MHz). The IF inductors/transformers at 10.7 MHz and 455 KHz have
disappeared from Digikey (used to be there a few years ago).
4) 2nd IF + FM demodulator. The Motorola parts (MC33xx) are gone. The part
that is found in many commercial XCVR is the Toshiba TA31136. This part is
not stocked by Toshiba's distributors in the US (12 weeks lead time if you
want to order 2K of them). Good news is that the Rohm BA4116FV is a
pin-to-pin compatible device and it is available at Digikey for $1.26. I
don't know if this part works since I have not seen it used anywhere...
5) 2nd mixer crystal. The 10.245 MHz crystals are easily available but not
the 21.4 +/- .455. This seems to remove the option of using a 21.4 MHz IF..
6) 2nd IF filter. The 455 KHz ceramic filters seem to have a very limited
availability. The exact type recommended by the IC vendor is hard to find..
7) FM discriminator. I could not find a source for the ceramic
discriminator recommended by Toshiba/Rohm (CDLBLA455KCAY24-B0 which is the
new P/N for the CDB450C24). I can understand the pain of the distributors
since every FM IC requires a different discriminator. The discriminator coil
that can be used instead is not easier to locate.
8) PLL: I am currently leaning towards National (LMX2306 or similar). They
are cheap and available. NS has a nice PLL design tool online but the tool
tries to convince me to switch to a better a part that I won't be able to
handle (leadless package). It is clear that the new generations IC's are not
designed for hand soldering at home...
9) Microprocessor and display: no problem here , plenty of choice.
10) TX chain transistors and PA Module: no problem with the regular vendors.
www.rfparts.com seems to have a large selection of modules.
11) TX low pass filter: will need to be hand made. That's OK but who is
selling tinned wire ?

Some notes:

1) I recently bought a dual conversion 72MHz RC receiver. For $45 (and 13
grams !), one can get one Toshiba TA31136FN, a ceramic discriminator, a
11.155 MHz (10.7 + .455) crystal, one 10.7 MHz crystal and one 455 kHz
ceramic filters, one IF transformer, 3 adjustable inductors, one dual-gate
mosfet (unidentified), a 3.3V regulator and more. I am not sure what to
think except that this might be a non traditional way to source 1/2 of the
RX section !
2) Some hard to find parts are sometime available as spare for Ham or
commercial radios but the prices are generally too high to be considered.
3) One way to go around the hard to find parts is to go with a more
discrete solution (no IF/Mixer/DEMOD/SQUELCH IC) and hand wire all the
inductors. This is not the way I am planning to go.
4) English is my 2nd language. Excuse the grammar mistakes and hard to
understand sentences.