Classy Steel leg band -
http://www.amazon.com/Pant-Cuff-Clip...5025053&sr=8-2
Cool light up leg bands -
http://www.amazon.com/Planet-Bike-Mu...7&sr=8-1-spell
Hebie Chain Gliders are, supposedly, easy to retrofit (full chain case) -
http://www.bikefront.com/products/chainguards
For something a little, less orthodox, you can take a page from ultralight backpackers and go with some ultralight gaiters:
Simblissity Levagaiter (needs long laced area but no other attachements) -
http://www.simblissity.net/levagaiter.htm
Or, if you REALLY want to look like you've got off the reservation - dirty girl gaiters -
http://www.dirtygirlgaiters.com/