Forgot to mention: if you want to use ABS plastic sheet available
ebay etc., say 1/16 in., it can be bent and formed using a clothes iron on medium setting (hottest will be harder to control). Never thought of because don't iron much anymore. Don't get any Neato plastic hot though, as it is the same melting stuff. I would bend it around a wooden dowel or pipe for a rounded corner. For sharp right angles around a wood bar. Tricky not to warp the side bent. Flatten with the iron after if needed. Easier to use the vinyl plastic in wall corner guard fittings which forms cold.
It is not necessary to make the entire strip in one piece; two halves meeting in the center of the front will do. This allows adjusting lengths after bending. With the vinyl it is easy to make a single piece bending on the Neato bumper itself without melting concerns.
I once tried to dry out a washed Roomba dust bin in a low temp oven; produces interesting modern abstract sculpture. I would not leave robots in a hot car in summer sunlight.
Laytex paint does not stick well to plastic. On cars they add a glue-like binder chemical to spray paint. In spray cans there is Krylon Fusion brand. Binders also sold separately. Advantage to wood bumper. Clear packaging tape can be used besides colored tape (and fancy patterns in duct tape now). Maybe stick on paper mailing label material and paint that (though might soak through ruining the glue, haven't tried).