You can also walk in to any mattress seller & ask for a customize super single. They will charge you the price of 20-30% more than the standard single size.

If you're not in a rush for it, you can wait for warehouse sales although the choices of model may be limited.

I bought a super/cali king bed from Dunlopillo warehouse couple of months back which is a 213 L X 190 W X 28 H dimension. Before I made this purchase, I've already set a budget of 4k for mattress + bed. Now, I've only spent 2/3 of that.

All mattress maker will cater your order but note that the maximum length they can do is only up to 200cm, I was told that their machine can only fit this size. I dunno how come mine can be more than that though.

The same guy who will sell you the mattress can also get the bed frame customized for the same 20-30% extra price. You can just select the bed frame design from their showroom or even catalog & they can do it for you.