Probably the little clip on the bottom that holds the blade on is bad. Typical issue. Don't know of any aftermarket blades available, but there may be some....
For a cheap quick fix: When I got my Elky, the PO had drilled a hole straight down through the blade into the post, and installed a large button head sheet metal screw. That was enough to hold the blade on, and if you get the right screw ( and do both) it looks almost like factory. If you ever get new blades, it will cover up the hole in the post like it was never there.