You can make a groover out of just about any airtight container- and ammo can (most sizes), or a plastic container. Things you'll need:
1. Two lids for whatever container you decide to use- one for a transport /on-river lid and another to install a flush valve and exit hose.
2. Go to and RV supply store and find the waste section. The large RV store in Denver has these items http://www.campingworld.com/stores/stores.cfm?store=27
3. Find a flush valve like this: http://www.campingworld.com/browse/s...19&skunum=3495
and install it on one side of your lid. Use liberal amounts of a silicone sealant. Install a PVC pipe for an waste tube http://www.campingworld.com/browse/s...9&skunum=21580
and secure it with a hose clamp. Again, use lots of silicone for all the spots you've drilled in your lid. The lid doesn't have to travel on the river, but it had better be pretty sealed up, or you might get the dreaded shit shower.
As for a cheap and very packable firepan, call up JJ at Raftin Styles in Salt Lake and have him sell you a 4'x4' welding blanket - I think they're about $40, and you can build a fire right on top.