Ideally you want to print this with a flexible PLA filament so that it will provide the same cushioning as the original rubber part.
I used the following settings on my Printbot+:
Extruder: 205 deg.
Bed: 85 deg. with ABS-juice coated blue tape
0.5 mm. extruder nozzle
0.3 mm. layer height
Cooling on constant after 1st 1.0 mm.
Print SLOWLY! Mine takes about 15 minutes per copy.
When done, just push the foot into the tubing and hey presto, good as new.
And a big shout-out to LucidOne for his excellent and elegant curve forming code here: http://www.thingiverse.com/thing:6455/#files. That made my job a lot easier.