Hyde and RGM cast-machined type braces have not been made-sold for years so only off the shelf type are tubular arch type are about it now. Everyone one and their sister says its very difficult to fit the Hyde or RMG type and I had so much trouble on Peel's, I thought I'd messed up the first brace so bought another then eventually new stanchions to get it working right. Sold off the spare brace. Best wishes enjoying the handling loads it takes to appreciate a brace benefit on Roadholders. I sure don't-won't on my un-tammed Combat.
The Cdo fender mount over the top and the struts from fork ends to fender definitely has some triangulation stiffening effect but rather minor compared to after market braces and unless you are practicing stoppies or dicing in-out of traction limits in go cart tight paved chicanes or rough off road playing I doubt you'd notice Roadholder twisting/rebounds even w/o any fender on to help tie legs together. I've experienced need of a force brace on Peel, but only going harsher than a modern fat tire cycle can even stick to develop those levels of fast changing forces on forks, then feels like rubber bands between pilot hands and axle/patch, so you twist one way to compensate staying in line but by then the rubbery forks are spring back so causes over reaction out of time of need to either crash ya right now or almost so must back off to recover in time and stop pressing your luck like that. This forum much respected at its population is in not the best resource for rare features, so suggest you go down World Wide list of vendors and see what they may have on items not worth listing anywhere as market so so small and even fewer able to install to work well. Might consider having one made, though in my dumb ass case I'd forgo any measuring devices not accurate to the nano-scale and make two halves then weld together while fitted.