You can get 6 gallon carboys on Amazon for $25e with free shipping.
As for kit vs. parts...I went to my local store (FH Steinbarts) and talked with someone there who made similar wines as I was planning, he helped me pick out what I'd need. I've had to go back once or twice to supplement that, but he was pretty thorough (just didn't think about things like a degassing rod). I've also bought a kit off craigslist from someone who never even opened it; looking through what it had in it, it was also pretty thorough, though slightly lower grade parts (plastic carboy, thinner syphon tubing, cheaper hydrometer, etc.).
My two cents? If you plan on making a batch or two of wine just to see if you can, and can get a cheapish kit, go with kit. If you plan on making this a long term hobby or pursuit, talk with someone and pick up quality parts. It'll be pricier (about twice as much) but it really does make a difference.