dunno about the first one, but http://www.voxengo.com/impulses/ has a lot of decent 16 bit ones for free and under a fairly unrestricted license (basically, no resell add copyright notice if redistributing blah blah).
they also have some software to help you with your second question, if you’re interested in that stuff.
or do it the ghetto way by playing a transient (a good fairly full frequency click or even just a dc pop type sound will work pretty well) that will trigger your 100% wet verb and record that output (render to sample in renoise), edit out the what’s left of the click in your rendered sample, re-save it, and there you go.
Incidentally, I made a personal lua script some while ago for the sole purpose of grabbing reverb impulses of vst reverbs. Might clean that up now that this convolution thing is booming.
One thing to note is that a convolution reverb cannot produce the modulation and variation that any advanced algorithmic reverb does. So, while it might sound convincing enough, you cannot really fully emulate this type of behavior with the convolution reverbs.
Also, when you figure them out they’re quite easy and fun to make yourself. Just google tutorials. There are a few smartphone apps floating around that automates the process, but I don’t know how good they are.
You can even try to use a percussion sample as IR if you are no going for a specicif effect but just experimenting. Claps and rimshots can work really nice to give a sound some really compressed space.