you can buy a K&B 48 hear in this link for $240. I believe they call this engine "the Screamer". I rather have it than any OS 40/46FX engine. just my opinion. you can buy other engines in this link too. but this 48 K&B seems to be the best buy. with mufflers the K&B should weigh close the same as your OS. they have the HP 40 too. but it's more money. both brands are super good engines, but old stuff I would have over a FX.
you can call them to see if they will build you a Webra. but I don't know if they have enough parts.
Model Engine Company Of America - America's largest producer of Model Engines for airplanes boats and cars (mecoa.com)
Jim