Have a look further afield if you really want a RHD drive car. I purchased a car from Australia (rhd) earlier in the year, its not perfect by any means, but has considerably less rust than a UK rhd car. I was looking for a UK rhd car, and all of the ones I looked at were circa 15k + and needed a considerable amount of money in body work/ rust repairs. I was quoted a further 5-7k for the work.
Converting a LHD as others have mentioned is another route, but unless you are doing the work yourself, it will be expensive. I was quoted well over 10k by a reputable firm to carry out the conversion, and the additional RHD parts, dashboard/steering column/rack/pedal box come with a hefty price tag.