Hi there Phil, welcome to oscarfishlover. Unfortunately, many people make the mistake of getting Oscars before they've actually done some research, you are certainly not alone stop I did exactly the same thing when I first Oscars. Anyway, you are here now and we can guide you in the proper direction.
There is a company called AC Aquatics. They manufacture Bespoke aquariums of all sizes and are very reasonable in price. I did have an issue with them when they built my 300 gallon tank. Now if it wasn't for the fact that they try to rectify the problem of actually refunded some money, I wouldn't be recommending them to. However, I think they deserve the benefit of the doubt since they didn't just tell me to get stuffed like some companies would.
Here's a link to their website. If you could, mention where you got their name from.
acaquatics.co.uk/