I've been playing around with adding various things to PR to attempt to modify it's physical characteristics. I've gotten interesting / encouraging results. One experiment actually ended up producing a cured resin that was like rubber. You could bend the rod of cured PR and even tie it in knots. Of course, the softer the resin, the harder it is to achieve a high gloss polish.
If you are interested in trying this for your faux ebonite, I would suggest you experiment with the following two things:
1) webbing solution added to PR. Available from PR suppliers (US Composites / Illstreet).
2) #6 plastic dissolved in your PR resin. (cut up plastic cup)
There didn't seem to be any hazardous or worrisome effects from adding either of the above to PR, but that doesn't mean there aren't any. Proceed with the reasonable cautions that experimentation demands if you decide to try this.
Ed