Black Rubber Bands?

[Peter Snow]

Hi Philip,

OK, don't laugh at this even though it sounds weird!

In my part of the world the local grocery store keeps the "stalk" type
vegetables (broccoli, cauliflower, etc) together in bunches with thick
rubber bands which may fit the knobs you require.  I just tried one on
the knob of my D4 and it is a little loose (and it's blue, though I have
seen black ones), but the thickness (depth) seems about right.  Anyway,
point is, these types of items often come from unexpected sources. If
your local stationery store does not have what you ewant, try the
grocery store!  

Cheers,
Peter