Here's a website in the USA that prints banners from your own artwork. http://www.victorystore.com/banner_pricing.htm
2ft x 6ft vinyl banners (the size I think would be most suitable for a conference booth) are $65 for one, $55 each for 2-5, $50 each for 6-10, etc. For an additional color, add 15%. (The current logo is black plus one color.) I suppose there's a shipping charge, and sales tax, but we're not talking huge sums of money. I would have ordered one in time for RegiCon if I'd realized there wouldn't be anything else. Whoever is going to the next conference should look into getting something like this.
No doubt there are other websites offering much the same thing. I've already found one in Australia, so if we need something for the MiniConf in Canberra, and no one has made other arrangements, we can get one from there. http://www.viscom.com.au/webcontent15.htm