aka... going nuts

The previous owner of my bike had swapped out the rear OEM indicators/turn signals for some cheap LED ones. When I got the bike checked before buying, one of them had failed somehow and the mechanic told the P.O. that the indicators were 'disposable' and he'd need to buy some more - so he just put the original ones back on.

The problem is halfway home I pulled in at the gas station and someone says "your indicator is falling off" - sure enough it was hanging loose, dangling in the breeze and looking mighty sketchy. I tried to get my fingers up inside the tail to tighten it but just couldn't turn the nut, so made do with twisting the indicator and holding the nut steady. This got it tight enough, but by the time I was home it had wobbled loose again.

I took the tail unit off and tried to tighten the nut, but there's just no room to turn it - the gap in the plastic is too small. Okay, looked in the manual and I can see that the P.O. has just used a standard M10 nut (14mm wrench size), rather than the flanged one shown in the illustrations. Searched multiple hardware stores before resulting to the bike shop and ordering the original ($4 a piece!) flanged M10 nut with 13mm wrench sizing. When I got the nuts though, the flanged part is 14 - so it still won't fit in the gap.

I've done a pretty thorough search here and not come across anything similar so figure I must be missing something. Has anyone else come up against this? I'll go back to the bike shop and check that they didn't order the slightly wrong number nuts or something - but it seems like a crazy design to have such a tiny tolerance in the small area in which to tighten the nuts.

I fiddled with this once long time ago when I took them off to put an LED one on.
I took the rear light and plastic off and used one of these cheap pipe sockets (like the cheap spark plug ones) , it fitted as it has thin walls and the wire goes trough it.
Use a spanner on the other side.
This from memory as it is long time ago I did this.

I couldn't wait for you lot to tell me what I was doing wrong so I took up the inelegant solution suggested by the mechanic at the local bike shop. He ground the flange off of the official KTM expensive nut that wouldn't fit, and I put that on with some loctite. It'll definitely hold but I know I've missed something here because there's no way these three OEM parts (Indicator, nut & tail unit) wouldn't fit together sensibly in some manner.

Eventually I'll get some flashy Rizoma flashers, but I have a motohooligan airbox to buy before then, and a bigger gas tank, and a..., and a...

Here's the bodge job....

The OE fixing parts are a nut welded to a stub tube and a shaped washer - check the parts fiche here.