Just got an idea...
There are numerous collections of sound effects on cd that are more than likely to contain laughter on them (I have a 300 sound one that I got circa the mid 90's for dirt cheap that has several laugh tracks on it). As long as your video isn't being distributed, sold, or shown on any kind of tv network (or anything else along those lines...I'm sure you get what I mean), this might be your best best.
Of course, the problem with this is that the laughter is the same each time.....