Are you looking to get some to compensate for the lift?
If so, I don't know if there are longer after-market ones available. Most people put in a spacer between the rubber bumpstop and the bracket. To know how big of a spacer you need to put in:
1) measure how far it is from the bottom of the bumpstop to where it contacts the axle
2) measure the amount of shock travel left (how much rod is showing)
3) subtract value #2 from value #1 and add about an inch (to make up for the rubber compressing, etc). That's how big of a spacer you need to fabricate.