Update for anyone wanting to do the same. I just found a shimano xtr m986 front mech that's rated 38-44 tooth max. It's 2x10 but I'm told it should shift fine with 11 speed rear derailure. From what I can find I suspect my slx shifter should work fine with it but don't quote me on that. It cost me £39 off ebay and that's a really good price but it's from Taiwan so could take up to a month to get it. Now Im going to get the strongest chainrings I can find and order a new chain. Hopefully everything goes to plan and shifts and fits properly and I'll update to let you know how it went and if it went to plan how it feels and preforms. If it doesn't go to plan I'll have some parts for sale