Ironraven,
Not trying to get you into the full press riveter or the journeyman model. Look at the hand setter tool for about $12.00 (not great but will set the rivets for less money than anything else I have seen). I would recomend the 1/4 inch rivets as they are easier to fit 550 cord/para cord through (you still wanting to just tie it to your pack?). You will need a hard surface you can hammer on with the hand setter. The one draw back is your rivets may split more on the side you crimp with this tool, though I have split a few on the arbor press setup i use.

Could you be more specific on leather rivets? I am not clear on which ones you refer to (screw and post, two piece). I have never tried other items, though I have seen some of the thick kydex (.093,.125) done without rivets for zero magnetic signature (I advise against this with steel blades).

Toaster ovens are ok and work if it is all you have. I have only used my regular kitchen oven. Set at about 350deg for about 5 min, pull out and set in a press contraption I made (4 bar clamps some plywood and 1 piece of 12x12 sheath making foam cut in half). I either open the window (windy days)or window and box fan to vent the area.

If you have a smallish sturdy table and small section of counter top to set up how you will press the kydex/knife sandwich, you have enough room to work this stuff.

Hope this answers most of you questions.
-Joe