can you pull the caliper and stick something in it to hold the piston in it (block of wood or clamp it or something)
move caliper around so the bleeder is the low point, then bleed them...
i always bleed by using vacuum hose from the bleeder to a jar and just run alot of brake fluid through the system.
^ just slowly pump the pedal from the drivers seat, make sure your MC doesn't go dry. then get out and close the bleeder snug with open end, then pull the hose off the bleeder and tighten the bleeder up tighter with the closed end.