-
Where are you based?
If you're in West London try W. H. Hanson : The sales guys can get a bit arsey if you don't know exactly what your on about but they can machine timber on site for you and you can sometimes get a deal on white oak if they have offcuts.
Or Moss & Co Very professional, high-end and expensive timber merchants. I only really use these guys when I need to find exotic hardwoods in a hurry. But their products are fantastic.
Personally I would head for Surrey Timbers A very good timber merchant that caters for hobbyists better than most. You can select your timbers from a pile in the warehouse and some of the stuff they sell is proper wood porn. It's worthwhile taking a block plane with you as some of the stuff will be rough sawn and you can plane it to check the grain ask before doing this they can dimension it for you for very reasonable prices and I think they will also join boards if needed.
If you need to use a biscuit jointer or domino I might be able to help.
By the way if you can find a board in the dimensions you want it is likely to be through cut and (unless it's very well seasoned) susceptable to cupping / shakes / bowing etc. so you'll probably be best jointing boards to your desired width.
Anyone got any recommendations on where I can gat some PAR white american oak in a wide width - approx 600mm x 800 x 32. 2 pieces biscuit jointed would be fine if needs be.