A left handed guillotine is not something we have come across as they are basically made for right -handed use with the blade on the right that has to be opened and closed with the right hand. There is really no way this type of guillotine can be used left handed.
It is possible to buy guillotines that have the cutting blade at the back and a bar at the front that can be pushed down with either hand (or both), but these tend to be more expensive “professional” models.
There are also a variety of rotary cutters that can be used with either hand but they are really more for decorative work and do not perform the function of cutting or trimming several sheets for paper with a straight cut.
You can see a selection of cutting tools suitable for left-handed use in our partner stores using thse links:
Cutting tools in the ALH UK Partners Shop
Cutting tools in the ALH USA Partners Store
Please add your thoughts on left handed guillotines as comments below and let us know of any sources for guillotines that work well for you.