Dewalt 4 1/2 Angle Grinder

[xxsckarterxx]

Hello to All.First off I'm new here so take it easy on me.I'm not really mechanically incline as most,but I try.I received a Dewalt 4 1/2 angle grinder from my wifes grandfather after he passed away. The actual Model is DW402 Type 2.My question is. I took off the grinding disk to replace it with what I call a sand paper flapper wheel for sharpening my lawnmower blades.The disk I took off was actually threaded on the spindle it self, so this means that apparently I'm missing the backing flange and the flange nut.My problem is everywhere I look up that model number the back flange or whatever it actually is, is discontinued.I need help!!!Are there universal parts or am I just SOL?

[Biggie]

I looked on e-replacement parts and it looks like the have the nut but not the backing plate, which looks to be a slightly differnet design than you see on most grinders.  I also see there might be some on ebay with a dw402 search. We've had dozens of grinders over the years and while different brands might be slightly different, i think all of our dewalts are interchangeable and in general most nuts and backing plates are somewhat universal.