In Indy you've got limited options but they could be reliable (I'm originally from the South Bend area but I went to school and have friends and family in that part of the state), the two that come to mind to me are 1st there is a Hobie dealer down there, they are called sailboats inc, not far off of the north part of 465, I met a guy named Charlie there, new parts and used boats there are dealer price $$, but they have a boneyard out back and might have some hulls, you could give them a call and ask, 1 317 872 7845.
The second bet is the Eagle Creek sailing club, I'd show up on a good sailing day and meet as many people as you can, in conversation let them know your situation, someone might have an extra set.
Third - http://www.thebeachcats.com/classifieds/catamaran-parts/p11967-1980-27s-hobie-16-for-parts-plus-trailer.html
Try this guy out, I've been want to go get that boat for a few weeks for parts just don't have the time.
Forth - If you don't mind a little bit of a drive, I live by the lake michigan coast, boats for parts are for sale up here all of the time on craigslist and what not, We could get in touch, find out what you are looking for and I could probably find you a older set of solid hulls for a couple hundred bucks and meet you in Indiana somewhere like Ft Wayne-ish, I have family in Goshen so I'm down there quite often. If it comes to that just send me a pm.