No dice man. You gotta take the whole slider/mounting assembly off. I know it's a pain in the ass to do, but for the effort, you can strip off all the flamables and have the cracks rewelded and reinforced for a LOT less than a new seat.
Trust me, between 2 Cherokee's, I've bought used seats, re-welded old seats, put the passenger seat on the driver side andjust had a passenger "space", Rewelded the mounting brackets... several times on some of those situations.
The only thing I haven't done is ponied up the dough for Aftermarket seats. The shipping on them for me is just effing insane. The price can easily double.
But if you have to, swap the passenger seat into the drivers side (yeah, you gotta switch brackets) and let someone else deal with the busted seat while you keep your passengers alive. Of course, you could take all the padding off and take it somewhere to fix it.
I've read in similar posts to this that sometimes upholstery places can weld the cracks? Must be nice to live in a city so big that couch stuffers have welders... I'd try an autobody shop or a boating supply/service place. but what the hell do I know? I just buy a co-worker a beer and he can re-weld his cracked welds every three months.
*Sigh* Stupid shipping.... I hate taking out those seats.