It isn't under $30 but it comes with nice crystal holders and a vase that can both be used after the wedding. Plus, the floating candle is a little different than the usual unity candle. They also have different ones on this website too.
I think I remember David's Bridal candle/holder sets for a decent price, but I forgot what the prices for the holders were since I still need to buy both candles and a holder You may want to check there.
Re: Unity Candle
I bought our unity candle a few months ago and didn't even think about a holder for it!
I'll be watching this post to see where people are getting theirs!
Missing Our July Sparkler
BFP-11/12/12, MMC 1/16/13-baby stopped growing @ 9wks, found out at 13wks, D&E 1/25/13
This ones under $15!
http://www.amazon.com/Hortense-B-Hewitt-Accessories-Scalloped/dp/B000OCGURQ/ref=sr_1_5?ie=UTF8&qid=1329941536&sr=8-5
This one's only $23
http://www.amazon.com/Darice-VL25-3-Piece-2-Taper-1-Piller/dp/B002PNUYZG/ref=sr_1_2?ie=UTF8&qid=1329941536&sr=8-2
Missing Our July Sparkler
BFP-11/12/12, MMC 1/16/13-baby stopped growing @ 9wks, found out at 13wks, D&E 1/25/13