You can do GHR's "ghetto style".
Here is a thread to get you started:
http://www.bodybuilding.net/powerlif...t=glute+raises
You don't have to do them exactly like in the pics but that should give you and idea of the basic idea. This will be much tougher than an actual machine. I workout at home so I do them off my high/low pulley station basically with my knees on the seat (with an extra pad).
If this doesn't work out for you you can also bridge the gap a little by combining leg curls and back extensions in a superset. The key to this is you do the back extensions using a tight and set lower back and focusing on hip extension via the glutes rather than lower back extension...pause a bit at the top for a nice tight finish. So back and forth between that and leg curls....
However, ghr's are much better than leg curls by about a hundred times. Back extensions, if done like I described (correctly
) are of course always useful.
P.S. when I say back extensions I mean "hyperextensions" as I see you are doing. I just don't like the 'hyper' term so I don't use the name. You may be doing them differently than I describe...