I'm pretty sure Permaplug and Masterplug are the same company.A couple of cheaper ones? Oddly Wickes states Masterplug but image Permaplug?
As for rewirable plugs that look similar to moulded plugs, how about https://www.rapidonline.com/sealey-pl13-320-resilient-plug-13amp-heavy-duty-pack-of-20-89-2054