A very good question indeed, many of us are in the same boat. I keep thinking that
someone out there has a replicating pantograph, or whatever they're called these days, and could turn out replicas from an existing forend. Or even make them from synthetic- that's how desperate some of us are to get the rifle back to something like original condition. In other words, don't be in a hurry, because this is likely going to take some time. I'm slowly getting the bits and pieces together, maybe one day I'll have a "bitser" SMLE of my very own.
ps- forgot to ask: is the barrel uncut, ie still 24.5" from receiver to muzzle? Because if it's less than that, it's not worth trying to restore.