Hi Mark

I haven't found anywhere yet that stocks them as standard. Dependant on the type of topper you want then a Super King one tucked under usually does the job. To be honest though, the join part really isn't all that noticeable to most people. If you roll over you can feel a change in tension where the two mattresses meet but its not the gully some people anticipate.  Try the mattress first and purchase a topper if required.

I hope this is helpful and if you would like any further information please do not hesitate to contact the office on 061 945 3757.

Kind Regards