Thanks junkie ! That's actually how this product was born, I needed one and couldn't buy it !
The ice hockey puck is a great idea, in fact, at least two places sell exactly that as a jack pad at a crazy price. The only problem is the thickness of the puck, it doesn't allow a deep enough slot for many applications and vulcanised rubber is much more likely to split, wear and be degraded by chemicals than polyurethane.