You might consider fabricating a new master cylinder lid or ordering one that already has remote fill capabilities, some pretty neat looking stuff out there.

Heres another easy way You could braze on a elbow on a old lid and put it on the master cylinder, get a old pump up sprayer and take off the wand and use hose clamps to clamp the hose to the elbow, fill the sprayer full of brake fluid and pump it up, put small hoses on the furthest bleeder first and crack it with the hose in a jar to collect the old fluid, the pressure will force the fluid all the way through (make sure sprayer always has plenty) and go through all the lines, unhook the sprayer and suck out a small amount so you can remove your modified lid and put your old lid back on, your done. Ok I wish I could take claim to this but I bought a power bleeder from Summtt and thats basically all it is, go to there web site and look it up if you want. best of luck Matthyj