Look in the yellow pages for a local Hydraulic shop or industrial supply. Then , as stated above, snip about a 1/2 inch piece off and take it in to the store. Tell them you want a coupler.
They will size it for you and will tell you how to splice the line.
You will want to make sure you have room for a coupler. If the line was cut during operation there might be a pinch point causing the failure. If thats the case then you might want to splice on either side of the pinch point with a new piece of line.