There's no simple way to refit the camera for electronic flash., because you need to get into the shutter and alter the aftermarket flash sync so it synchronizes with electronic flash, rather than bulb flash. I don't know how to do this.
Afterward, you could find an accessory shoe from a camera bracket, drill some holes and bolt it to the side of the camera. You'll be limited to the size of the flash, because of the weight of the flash unit.
Rolleiflexes weren't mean to have a flash bolted to the side of the camera, and as you know the early cameras weren't intended for flash. The later flash-enabled cameras work best when attached to a flash bracket.
You could buy a later Yashica TLR that has a shoe on the side of the camera and use that.