Jeff,
Just saw the reflect-a-boot. May help, but only if you have no contact (if you have contact with the boot or sleeve, you're hosed). You could take some red hi-temp RTV and glue a couple wraps of aluminum foil around one of your current boots and achieve the same thing for a test period (may be a little ugly, but it is a test). If it works great, buy the real ones. I suspect the reflective part will only be a marginal improvement over what you already have, but I've been wrong a couple times today already
.