Hi, posting this more of a help to others as I spent some time googling and looking at options to change the brakes. I have a radwagon 4 that came with the radius brakes, for a while I had an issue where when pulling one of the brakes the lever would go all the way to the bars, if I let go and pulled again this time the brakes would work. I tried sorting it but I've never been a fan of mechanical disks.

I picked up a pair of Magura MT5e brakes, these are the ones labelled HIGO-Closer (I believe that is important for being compatible with the radwagon electronics). The brakes came already setup on circa 2m long hose so no problem getting to the rear wheel.

These went straight onto the bike no problem, I kept original discs and used the same bolts for the new callipers, wiring ports plug in fine to maintain the brake light operation.

I did cut the hoses down as they were longer than needed so had to rebleed but that was easy enough if you are familiar with doing it. Only alteration I made was to file a groove out of the clear rear wheel guard to allow the hose a better entry angle.

Brakes are so much better than original, feel safer riding knowing I can stop quicker. I picked the brakes up for ?135 on eBay for the pair which seemed pretty good. 

For some longer rides our kids get tired on their own bikes, so to have the option of them riding their own bikes but jumping onto the wagon I knocked up this, using the axle packaging adapter that came in the boxing. Just bolted through the plastic. As it's just pulling (kid not on bike) the plastic seems more than robust. The cable tires were just incase anything came loose.

It does obscure the rear light even without bike attached though.

Really easy thing to do for an extra option on bike rides. New here so maybe this has already been done?