No prescription is required to buy nebulizer parts. You can call most places and they will process your order if you explain it is for your already existing neb.) Basic Medicare Part B does not pay for the parts. Depending on any supplemental plan(s) you may have, a nebulizer may be covered as durable medical equipment, but my plan only covers a very basic, corded machine - nothing portable or battery operated, and no replacement parts. Another tip - I buy several at once, to get to the minimum so I don't pay shipping. I used to share them with my friend, who has since passed away. Now I share with my daughter.
On my Blue Cross plan through my former employer, which happens to be my Medicare supplement, my nebulizer solutions are covered under Medicare B because they are used in medical equipment. Medicare Part D does not cover them. (I have this "discussion" every 3 months with my mail order pharmacy or Walgreens, depending where I order - they submit to Part D, get rejected, call me, I tell them to resubmit under Part B...)
My saline costs about $10 for a months supply, or $20 for 3 months through mail order pharmacy with a prescription. Lots cheaper than on-line.
Sue