Here is a little, quick and very cheap mod that I have done to my unicycle (soon to be both when I get the time) - wish I had done it when I first bought the cycle as I hate with a passion the scuffing that occurs when she gets dumped on the ground from time to time in practice.
Don't get me wrong - when I am a lot better with my rides (and it's coming) this can come off but if it can save some cash or your ride looking scruffy then this might be of interest.
Step 1: Materials and tools
Nothing really needed - some fairly high density foam - I cut a section from those sausage shaped float kids use in the pool - like taking candy from a baby - woooooaaaa ha ha ha ha - evil laugh - - no not really, I had a bit laying around (or did I)
About 40mm of old cycle inner tube (wide like in mountain bikes) - your local cycle shop will probably have some of these being thrown away if they do repairs and might let ya have them for free (mine does).
Pair of scissors and a knife to cut the foam
Step 2: Then
cut a length of foam that is the same distance as the plastic bumper and if required like me, shape to have a flat side (measured from underneath) + about one and a half inches.
Slip the tube of inner tube over the plastic bumper till it meets the seat.
Shove the foam into the inner tube too - the contour of the plastic bumper underneath locks things in place a treat.
Not pretty but it saves damage - you can see the pounding it has taken already.
Be safe DZ