I bought one of these to get into a full face flip up for cheap - $140
http://www.webbikeworld.com/r2/motorcycle-helmet/vega/summit-xpv.htm
The inner pads come out very easily, and one can add or subtract filler or foam to create a custom fit. A Winter face mask / breath diverter to keep fog off the shield is available for $8, as is an electric dual lens shield for snowmobile use.
After owning one, I like it enough that I'd buy another if the need arose. It's comfortable now that I adjusted a few liner pads, and also added a quick disconnect strap buckle.
http://motorcyclehelmets.net/yvs500/shopexd.asp?id=31
They tend to run a little small - I wear an XL Shoei, but needed a 2XL in the Vega.
