Best of luck. Were there ever a bunch of K1300GTs around? Great bike, perhaps one of the best BMWs of the decade, but they stopped making them after only a short time. There are a couple of used Corbin K1300GT seats on the US ebay site, (
LINK), but that's no RDL and the prices are high enough that it would be better to send your own seat in, though the shipping sucks from the UK.
The second one was front/rear for $675 usd.