Your best option is to post an ad offering to trade your low for a standard rear, you may get lucky. Next is to just buy a normal (or Adventure) seat from someone here or on the MOA classifieds which is what I did. Found a basically new set F&R for $200. There is a market for low seats so you'll be able to sell it. For instance there are riders who want an extra one in order to send off to be redone by Mayer, etc.
I'd say at worst it'll cost you maybe $100 to change seats and you should factor this in.
2015 Road King