Here you go, this page should satisy at least some of your Guillotining needs. There’s a blueprint available for a 1/5 scale 1792 model guillotine, but it costs $35. AND you’d have to build it yourself, but it’s a start. (Plus, you can always scale up or down the blueprints to build your guillotine to an appropriate size)
There are also model guillotines on eBay fairly often.