I would never hesitate to buy from ardennes. They are great people and the price and shipping exprience I had was awesome. I got a Les Lat hybrid bout approximately 7.5"x 1.5" with large slurry stone for what I feel was a very good price. Got here in no time considering the distance. I think it took a week or less from shipping date. This is a great stone and a great deal. Unfortunately it was also the last Les Lat they had. I don't think they are finding anymore right now. Maybe next year. If you tell them what you are looking for and that it is for a razor they will look through what they have for a nice one for you. They sent me pics so I could decide if I liked also.
Anyway if you don't want large and rectangular, you can get a great deal on a bout from them or even TSS.
Also I have had great results with old vintage stones I found at very good prices online. You need to look alot though and have a price you are willing to pay and be willing to just let it go, cause a lot of people are willing to pay way more than I was(some people have serious HAD). Also look read and learn about what characteristics usually make up the kind of stone you are looking for. When looking at vintage stones you will see what I mean.
All that being said if you are set on a large 8X3 stone you will pay a good bit, but can still get a good price on a bout.