Bigcountry. I'm running into the same trouble you did. Here's the fruit of my labors:
Midway has some "dangerous game" slugs and a something else wich is nothing more than a .730 ball with fins stuck on the end. Both about $0.50 a piece. Neither one hold much appeal to me.
http://www.lightfieldslugs.com/lightfield/estore/index.cfm?catid=23&id=2&cfid=10202807& cftoken=96170633
sells just the Lightfield IDS sabot slugs at about $0.80 a piece. A big step up...but I've hears and seen first-hand some questionable stories about there terminal performance. (Deer shot quartering towards me at about 70yards. It ran about 80yards. No shoulder-bone hit and still didn't exit. I clipped the trachea as well. Found four little chunks of lead that wieghed 250-ish grains. Those chunks came from a 1 1/4oz (that's around 550grains) slug.
)
There's also something out there called "blue-force" sabots are something like that.
Nothing in the form of true "roll your own" sabots that let you chose the actual projectile.
Also if your still interested in trying it or just plain messing around with slug guns again you need to check up on shotgunworld.com under the "Slug Gun" section inthe forums and then
http://xsorbit31.com/users5/slugshooting/ which is the forums at slugshooting.com
I did run across a company called Dixie Slugs. $7.50 for 5...but you have to order 5 boxes to offset shipping costs. They make two or three different types. We're talking
hard-cast sabots in the 700gr-600gr area going around 1400fps. These things look ideal...EXCEPT I'm not ready to spent $40 without knowing how accurate they are. (I'm gonna work on getting my buddy to split an order with me
)