Rear carrier number plate assembly

I finally decided to install the rear tyre carrier. Its been in my shed for around 4 years (dont ask how I used to carry 2 spares, tubes etc without a rack :) . So, mission completed until I realized I had forgotten to relocate the number plate. So, off to an aftermarket mob and "yes we can get one, no light, $77). No thanks, so I accumulate the bits (ha ha) and away I go.
This isn't going to work. It's not a boat, I need to fix it to the carrier. Hmm...how do the Kmar people do it ? Can't find any pix. Can't find any prices of the Kmar one (and not sure it will fit anyway).
Can't do the shopping tomorrow, the vehicles illegal....no worries, TIE the number plate on, it will do for a quick daylight trip...yes officer I have my excuse all prepared.
I guess I need some visual details (and possibly pricing) on a commercial one (that way I know it wont disintegrate on those holes and corros).
Could any kind, knowledgeable soul point me in the right direction ?

PS I know its a vehicle post, but the vehicle does get out there.