Mad Robot, Victoria Minis and Anvil Industries should be your go-to's for any
IG project!
Your thread title reminded me of some Russian chap who sculpted some pretty cool Valhallan stormtrooper models a few years back... I doubt they were ever produced in any great quantities but as an idea for what you are looking to do, here ya go...
For some strange reason i really like the second guy's helmet design! The third trooper is something slightly different to the accepted greatcoated Valhallan aesthetic of course but it's still a pretty good concept and wouldn't look out of place next to your regular grunts...
But anyways, the look of the first 2 models could be very easily recreated using bits from any of the 3 aforementioned great companies, good luck!