I use only 5 gallon buckets almost exclusively. I do about 4.75 gallons in each one, I just keep a clean airlock setting in sanitizer ready to swap out once a day for the first few days as/if needed.
I usually just buy the white buckets from Wal-Mart but a bakery bucket is great, and most bakeries practically give them away!
For the lids, I use ones that came with my 6.5s, or I buy some from Wal-Mart or the hardware store. I drill a hole, and I have a big store of grommets I bought at the hardware store. If the lid doesn't fit super air tight it's no biggie, may not see as much airlock activity, which is fine if your pushing the volume limits like I do. I've seriously been using these for a hundred batches, cheap and effective.