Public speaking
LOL... I'm sure you'll do great!
I can't exactly vouch for costs, but we have had several banners and signs created for my organization (made by a local friend who is very reasonable). He actually does vinyl decals on a vinyl banner (rather than printing on the banner) and that may be why he's more reasonable, I'm not sure, but they seem to be fairly durable and storeable. I just did a very quick search online and the ones I looked at seemed to be fairly reasonable ($3 - $8 per sq. foot at one site). I guess it depends on how large you'd like it to be and I doubt you'd need a very large one for a tradeshow booth.