You don't need a bar if you don't want one. Just use dumbbells like in XTRAIN, she only uses dumbbells in that series. There are a lot of exercises that I sub DB instead of a BB. It just your preference and whatever feels good to you. If you have DB that go heavy enough for you, than you are set.
Thank you! I know the target close to me does not carry barbells and plates. I'll check Walmart and/or do some searching online.I would say check out a used sports store if you have one near you or Walmart/Target. They usually have sets that give you a bar and about 50lbs or so in plates for around $50. I've asked Cathe before about subbing DB for a BB and SNM responded that it's always a personal preference. Best of luck and Happy New Year