Have a look on guntrader under equipment search. Derek Lee gunsmiths has a browning b25 stock and forend for £250 might need a bit of fettling but would have thought the stock would fit if not the forend.
I have a r/h 15ins sporting stock for a Miroku. It has a comb-raiser too. Nice figured wood with an oil finish, plastic butt plate. Originally came off a Browning Waterfowl 425, it had a rubberised finish. This has obviously been removed and the wood re-finished. It won't be expensive.Contact me via email and we can talk if you're interested.[email protected]