for most things, jacks seems to have some really good prices. the downside, there is no real time inventory
parts tree seems to have better parts diagrams, but again, no real time inventory
e-replacement parts has real time inventory which is fairly accurate, but not as good of prices.
local dealers sometimes are best so as to not deal with shipping, but mine have very little inventory
Bob @ Ashokan Turf and Timber knows his stuff better than anyone I've met. if you are going to be buying a couple oem parts, call him, shoot the bull for a bit, and pay whatever he wants... its worth it...and he's reasonable anyway.
EBAY ... sometimes you can do really well on ebay, sometimes not. the biggest benefit to ebay is that if its on ebay, it probably IS in stock. unlike jacks which is a crapshoot
last jacks order ended up coming in 3 pieces. I was waiting for some stuff for a number of weeks, and called them and they noticed how long i was waiting. they shipped stuff separately without charging me extra.