if you have a bench grinder you can cut it with that just a little more trouble

 

allen bits from a drill driver might work as well.

 

I have cut many an Allen wrench with a metal cutting bandsaw. You might try a hackswaw.

 

I just took the allen head bolts out and put in hex head bolts much easier.

 

I keep cut down allen wrenches in my box. I have needed and used them countless times over the years. I have a rule. I buy or make any tool I ever need and keep it in my tool box. If I need a tool once, chances are I'll need it again. I haven't used my British Standard Whitworth wrenches and sockets in a long time but if I ever need to work on an old Limey, I'm ready.

 

Yup, and lockwashers