Controllers are easy to find, they pop up on amibay and ebay all the time. The expansions are not - they are not readily available and you'll be paying quite a bit for an SX-1, and a shitload of money for an SX-32 and especially an SX-32 Pro Module. A CF->IDE kit is easy to buy, you can buy one from amibay readily, and gotek floppy emulators are also abundant. To get a complete setup like I describe, you're going to be paying a few hundred dollars after shipping and if you go for stuff CIB like I did.
Thing is, you don't need any of this stuff to play amiga 1200 and amiga 500 games on your CD32. Like I said, there is a movement to convert the normal non-CD amiga library into self-booting CD32 formatted games, and you can very easily find ISOs for compilations containing 222, 444, or 888 games on one CD.
Also worth noting - not all games use a CD32 pad. Most Amiga games use standard 1-button or 2-button atari joysticks. My favorite "amiga" controller is this:
melts into your hands, so comfortable. It uses microswitches and feels really great. My second favorite?
The Amiga Gravis Gamepad. These things rule for one specific reason - there is a switch on the bottom. When it's to the left, the red and yellow buttons are buttons 1 and 2, and the green and blue buttons are turbo versions of buttons 1 and 2. When the switch is to the
right, the red and blue buttons are buttons 1 and 2, and the yellow and green buttons are
up and down. This gives you a dedicated jump button in many Amiga games that feels great. Using up to jump feels good with a nice joystick, but it never feels right with a gamepad IMO. The Amiga Gravis Gamepad fixes that problem.
You can also mod a sega master system pad easily to make the second button map to up, but some games use 2 buttons anyways.
The cheetah bug, and gravis gamepads aren't hard to find. I have 2 stock CD32 joypads, 2 competition pro CD32 pads, 2 competition pro joysticks, 2 zip sticks, 2 cheetah bug sticks, and 2 amiga gravis gamepads.