Spare parts are easy to come by, but if you want to get a Romy for spare parts DPH Arms is selling $80.00 complete romy grade "C" kits right now. http://dpharms.com/grade-c-kits-p-128.html
There are alot of places to get a Romy kit from, but I would suggest supporting one of this sites advertisers.
You'll need a receiver along with your kit to complete your AK. I suggest a Global receiver. I got mine from Ohio Rapid Fire.
You need a total of 6 US made parts in your build to make it 922 compliant. Fire Control Gruops count as 3 parts, your receiver is another. Changing the pistol grip will count as your 5th, and a simple furniture change will get you your 6th. Or you could get US made magazine followers or a bunch of other US parts available. (Theres a post that lists all of them here)
The AK is a very simple mechanism, and doesn't need "spare" parts always available. Barrels are pretty hardy (especially for civilian use) and should last you for years. You could get a spare gas piston (I'd count for another US part) as well as bolt/carrier but all in all the AK's don't 'wear out' many parts easily.
Don't forget a good hammer, drill press, and Dremel. They will come in handy.
Good Luck.