I have a DMR jump seat but ............... i ripped the padding off it, its not like on a trials bike it gets used that often, its reasonably comfy to plonk my arse on if its really needed.
just get a cheapish, slim profile saddle rip the padding off and use that, i say never really noticed much difference, as you can buy saddles in the same style for use on road bikes except there carbon jobbies, but on a trials bke you hardly need the comfort.
Soencer