I have done them before, but I haven't ever bruised from it. Do you normally bruise easily? Maybe you could fold a towel and put it over the pad or just do deadlifts.
Swiss ball is one option. That works well. Or if you have a high bench, that will do the trick. In my gym, there is this apparatus for leg raises. The angle can be adjusted ... so, when it is set at parallel (to the floor), It is about waist high off the ground. Great ROM. If I want to use weight, I'll jut stick a dumbbell between my ankles. Works fine.
I don't do them anymore. I feel that deadlift hit my lower back just about as much as I can stand. It get's so pumped from just deads that is uncomfortable borderline painful (in a good way of course).
Pullthroughs can be an alternative, No machine should bruise you IMO-unless you use absurd amount of weight. SLDL, pullthroughs, Gm's or Zero's suggestion